Pierre Vadim Carlo Di Pierto Essays in Empirical Asset Pricing Eine Dissertation, Northwestern University. Verfahren zur Paarung von Wertpapieren, wobei das Verfahren umfasst: Empfangen, durch einen programmierten Computer, eine Anforderung, mindestens zwei Beine von unabhängigen Wertpapieren zu koppeln, wobei jede Sicherheit einer anderen Asset-Klassenidentifikation zugeordnet ist, durch einen programmierten Computer , Eine erste Sicherheit von einer ersten Assetklasse, die einem ersten Bein zugeordnet ist, durch einen programmierten Computer eine zweite Sicherheit von einer zweiten Assetklasse identifiziert, die mit einem zweiten Bein assoziiert ist, das durch einen programmierten Computer bestimmt, ob der erste Bein und der zweite Bein sind Handelsfähig als Paar und Erzeugen eines angeforderten Paares der nicht zusammenhängenden Wertpapiere durch einen programmierten Computer, wobei das erzeugte Paar durch eine eindeutige Kennung repräsentiert wird. 2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, dass das Ermitteln, ob der erste Schenkel und der zweite Schenkel handelbar sind, in Betracht, ob eine ausreichende Liquidität in einem Markt für den ersten Schenkel und den zweiten Schenkel vorliegt. 3. Verfahren nach Anspruch 1 oder 2, dadurch gekennzeichnet, dass bei der Bestimmung, ob der erste Schenkel und der zweite Schenkel als Paar handelbar sind, berücksichtigt wird, ob vordefinierte Kriterien erfüllt sind, um eine Beziehung zwischen dem ersten Schenkel und dem zweiten Schenkel herzustellen. 4. Verfahren nach Anspruch 3, dadurch gekennzeichnet, dass das angeforderte Paar erzeugt wird, wenn sowohl eine ausreichende Liquidität vorhanden ist als auch die vordefinierten Kriterien zur Festlegung einer Beziehung erfüllt sind. 5. Verfahren nach einem der Ansprüche 1 bis 4, dadurch gekennzeichnet, dass die Speicherkomponente (1, 2, 2, 3, Assetklasse eine erste Sicherheit von einer ersten Assetklasse identifiziert, die einem ersten Bein zugeordnet ist, eine zweite Sicherheit von einer zweiten Assetklasse identifiziert, die mit einem zweiten Bein assoziiert ist, bestimmen, ob der erste Bein und der zweite Bein als Paar handelbar sind und das angeforderte Paar von Wobei die erzeugten Paare durch eine eindeutige Kennung repräsentiert werden. TECHNISCHES GEBIET Ausführungsformen der Offenbarung beziehen sich allgemein auf Finanzhandelssysteme und insbesondere auf ein Paarhandelsystem und - verfahren. HINTERGRUND Pairs Handel ist eine Strategie, die von einem Trader verwendet wird, um einen Return on Investment zu generieren, indem er einen Spread zwischen zwei verwandten Wertpapieren, typischerweise in demselben Sektor, vorstellt, die dazu neigen, zusammenzuziehen, wobei der Trader eine Long Position und eine Short Position auf der Zwei verbundene Wertpapiere im Paar. Traditionell wird der Handel von Paaren unter den Wertpapieren auf demselben Markt oder, im Umgang mit Optionen, unter Verwendung desselben Basiswerts gehandelt. Jedoch gibt es derzeit kein Handelssystem, das für den Paarhandel von nicht zusammenhängenden Wertpapieren aus verschiedenen Anlageklassen sorgt. Somit können Händler, die nicht zusammenhängende Wertpapiere, möglicherweise über verschiedene Anlageklassen, handeln, dies nur tun, indem sie separate Aufträge für jede der nicht verbundenen Wertpapiere mit der Hoffnung ausführen, beide Aufträge zu den Zielparametern in der gewünschten Zeitspanne auszuführen. Leider macht der getrennte Auftragsansatz für die Durchführung eines Paarbetriebs den Händlern ein Beinrisiko und eine Liquiditätsfragmentierung ausgesetzt. Dementsprechend besteht eine Notwendigkeit für eine Handelsplattform, die zum Paarenhandel von nicht verbundenen Wertpapieren aus einer oder mehreren Vermögensklassen unter Verwendung einer Einzelpreisbewegung, die durch einen Einzelauftragsansatz bereitgestellt wird, angepasst ist. Die vorliegende Offenbarung stellt computerimplementierte Verfahren und Systeme zur Leitung von Paartrakts bereit. In einem exemplarischen Ausführungsbeispiel kann ein computerimplementiertes Verfahren gemäß der vorliegenden Offenbarung das Vorsehen einer Vielzahl von vordefinierten Paaren nicht zusammenhängender Artikel umfassen, die eine Auswahl eines vordefinierten Paares aus den vordefinierten Paaren für einen Paar-Handelsauftrag empfangen, wobei sie in die Paare-Handelsorder eintreten Einen einzelnen Auftrag in einem Auftragsbuch, Bestimmen, ob Auftragsparameter, die einem ersten Schenkel und einem zweiten Schenkel des vordefinierten Paares zugeordnet sind, erfüllt sind, und anschließendes Ausführen der Paarhandelsordnung, wenn die Auftragsparameter, die dem ersten und dem zweiten Schenkel zugeordnet sind, beide erfüllt sind . In einer anderen beispielhaften Ausführungsform kann ein computerimplementiertes Verfahren gemäß der vorliegenden Offenbarung ein Empfangen einer Anforderung zum Koppeln mindestens zweier Beine von unabhängigen Wertpapieren umfassen, die jeweils einer anderen Assetklasse zugeordnet sind, Identifizieren einer ersten Sicherheit von einer ersten Assetklasse, die mit a assoziiert ist Ermitteln, ob das erste und das zweite Bein ein handelbares Paar bilden, und das Erzeugen des angeforderten Paares nicht zusammenhängender Wertpapiere, wobei das angeforderte Paar durch eine eindeutige Kennung repräsentiert wird. Ein beispielhaftes System gemäß der vorliegenden Offenbarung kann eine Speicherkomponente und eine Verarbeitungskomponente umfassen, die konfiguriert ist, um die verschiedenen Verarbeitungsschritte und Merkmale auszuführen, die oben und in dieser Offenbarung beschrieben wurden. KURZBESCHREIBUNG DER ZEICHNUNGEN Die vorliegende Offenbarung wird beispielhaft und nicht beschränkend veranschaulicht und wird unter Berücksichtigung der folgenden detaillierten Beschreibung in Verbindung mit den beigefügten Zeichnungen, in denen sich gleiche Bezugszeichen auf gleiche beziehen, deutlich In denen: Fig. 1 ist ein Blockdiagramm, das ein beispielhaftes Computernetzwerk darstellt, in dem Ausführungsformen der vorliegenden Offenbarung arbeiten können. FEIGE. 2 ist ein Flussdiagramm, das eine Ausführungsform eines Verfahrens zum Paaren von nicht verbundenen Wertpapieren von einer oder mehreren Assetklassen darstellt. FEIGE. 3 ist ein Flussdiagramm, das eine Ausführungsform eines Verfahrens zum Handel von Paaren nicht zusammenhängender Wertpapiere aus einer oder mehreren Assetklassen darstellt. FEIGE. 4 eine schematische Darstellung einer Maschine in der beispielhaften Form eines Computersystems. DETAILLIERTE BESCHREIBUNG Ausführungsformen der Offenbarung stellen ein System und Verfahren zur Durchführung von Cash-Equity-Paaren-Handel bereit. In der folgenden Beschreibung werden zahlreiche Einzelheiten dargelegt. Es ist jedoch für den Fachmann offensichtlich, dass die vorliegende Offenbarung ohne diese spezifischen Details ausgeführt werden kann. In einigen Fällen werden bekannte Strukturen und Vorrichtungen in Blockdiagrammform und nicht im Detail gezeigt, um die vorliegende Offenbarung nicht zu verdecken. Einige Abschnitte der detaillierten Beschreibungen werden in Form von Algorithmen und symbolischen Darstellungen von Operationen auf Datenbits in einem Computerspeicher dargestellt. Diese algorithmischen Beschreibungen und Darstellungen sind die Mittel, die von den Fachleuten auf dem Gebiet der Datenverarbeitung verwendet werden, um die Substanz ihrer Arbeit am effektivsten anderen Fachleuten zu vermitteln. Ein Algorithmus ist hier und wird allgemein als eine sich selbst konsistente Folge von Schritten konzipiert, die zu einem gewünschten Ergebnis führt. Die Schritte sind diejenigen, die physikalische Manipulationen physikalischer Größen erfordern. Normalerweise, wenn auch nicht notwendigerweise, nehmen diese Größen die Form von elektrischen oder magnetischen Signalen an, die gespeichert, übertragen, kombiniert, verglichen und anderweitig manipuliert werden können. Es hat sich zuweilen als günstig erwiesen, hauptsächlich aus Gründen der gemeinsamen Nutzung auf diese Signale als Bits, Werte, Elemente, Symbole, Zeichen, Begriffe, Zahlen oder dergleichen Bezug zu nehmen. Es sollte jedoch beachtet werden, dass alle diese und ähnliche Begriffe mit den entsprechenden physikalischen Mengen assoziiert werden sollen und lediglich praktische Etiketten sind, die auf diese Mengen angewandt werden. Sofern nicht ausdrücklich aus der obigen Diskussion hervorgeht, versteht es sich, dass in der gesamten Beschreibung Diskussionen verwendet werden, die Begriffe wie Empfangen, Bestimmen, Erzeugen, Präsentieren, Auswählen, Routing, Anpassen, Ausführen, Füllen, Löschen, Verarbeiten oder dergleichen verwenden , Beziehen sich auf die Aktionen und Prozesse eines Computersystems oder einer ähnlichen elektronischen Rechenvorrichtung, die Daten, die als physikalische (elektronische) Größen innerhalb der Computersystemregister und - speicher dargestellt sind, in andere Daten, die in ähnlicher Weise als physikalische Größen innerhalb der Computersystemspeicher dargestellt sind, verarbeiten und transformieren Oder Registern oder anderen derartigen Informationsspeicher-, Übertragungs - oder Anzeigevorrichtungen. Die vorliegende Offenbarung bezieht sich auch auf eine Vorrichtung zur Durchführung der Operationen hierin. Diese Vorrichtung kann speziell für die erforderlichen Zwecke konstruiert sein oder sie kann einen Universalrechner umfassen, der selektiv durch ein im Computer gespeichertes Computerprogramm aktiviert oder rekonfiguriert wird. Ein solches Computerprogramm kann in einem computerlesbaren Speichermedium gespeichert sein, wie z. B., jedoch nicht darauf beschränkt, jede Art von Disk, die Disketten, optische Platten, CD-ROMs und magnetooptische Platten, Nurlesespeicher (ROMs) (RAMs), EPROMs, EEPROMs, magnetische oder optische Karten, Flashspeichervorrichtungen einschließlich USB-Speichereinrichtungen (z. B. USB-Tastenvorrichtungen) oder jede Art von Medien, die für die Speicherung von elektronischen Befehlen geeignet sind Der mit einem Computersystembus gekoppelt ist. Die hier dargestellten Algorithmen und Anzeigen sind nicht inhärent auf einen bestimmten Computer oder eine andere Vorrichtung bezogen. Verschiedene Mehrzwecksysteme können mit Programmen gemß den hierin beschriebenen Lehren verwendet werden, oder es kann sich als zweckmäßig erweisen, mehr spezialisierte Vorrichtungen zum Durchführen der erforderlichen Verfahrensschritte zu konstruieren. Die erforderliche Struktur für eine Vielzahl dieser Systeme ist aus der obigen Beschreibung ersichtlich. Zusätzlich wird die vorliegende Offenbarung nicht mit Bezug auf irgendeine spezielle Programmiersprache beschrieben. Es versteht sich, dass eine Vielzahl von Programmiersprachen verwendet werden kann, um die Lehren der Offenbarung, wie hierin beschrieben, zu implementieren. Die vorliegende Offenbarung kann als ein Computerprogrammprodukt oder eine Software bereitgestellt werden, die ein maschinenlesbares Medium mit darauf gespeicherten Instruktionen enthalten kann, die verwendet werden können, um ein Computersystem (oder andere elektronische Geräte) zu programmieren, um ein Verfahren gemäß dem Verfahren zu durchführen Vorliegender Offenbarung. Ein maschinenlesbares Medium umfasst jeglichen Mechanismus zum Speichern oder Übertragen von Informationen in einer von einer Maschine (z. B. einem Computer) lesbaren Form. Beispielsweise enthält ein maschinenlesbares (z. B. computerlesbares) Medium ein (z. B. ein computerlesbares) Speichermedium (z. B. Festwertspeicher (ROM), Speicher mit wahlfreiem Zugriff (RAM), Magnetplattenspeichermedien, B. Flash-Speichervorrichtungen usw.), ein maschinelles (z. B. computerlesbares) Übertragungsmedium (nicht fortpflanzende elektrische, optische oder akustische Signale) usw. 1 ist ein Blockdiagramm, das ein beispielhaftes Computernetzwerk 100 darstellt, in dem Ausführungsformen der vorliegenden Offenbarung arbeiten können. Bezug nehmend auf Fig. Wie in 1 gezeigt, kann das Computernetzwerk 100 aus einer Paar-Handelsplattform 130 bestehen. Eine Vielzahl von Trader-Rechenvorrichtungen 122A-122N, die geeignet sind, Trades durchzuführen, die hier zusammenfassend als Trading-Einheiten 120 bezeichnet werden können. Und Marktsysteme, die mit dem Regulierungshandeln einer Vielzahl von Assetklassen wie etwa den ETFs 142 verbunden sind. Aktien 144. Waren 146 oder einer anderen geeigneten Assetklasse, die alle hier zusammenfassend als Assetklassen 140 bezeichnet werden. In einer Ausführungsform können die Rechenvorrichtungen der Handelseinheiten 120 und die Marktsysteme der Assetklassen 140 kommunikativ mit einem oder mehreren Netzwerken (nicht gezeigt) zum Senden und Empfangen von handelsbezogenen Daten gekoppelt sein. Netzwerke können ein privates Netzwerk sein (z. B. ein lokales Netzwerk (LAN), ein Weitverkehrsnetz (WAN), ein Intranet usw.) oder ein öffentliches Netzwerk (z. B. das Internet). Die Paar-Handelsplattform 130 kann aus einem oder mehreren Modulen bestehen, die konfigurierte Aktivierungs - und Prozessaufträge betreffen, die sich auf die Anforderung von Paartraktiken beziehen, die von den Händlerentitäten 120 empfangen werden. Zum Beispiel kann die Paartauschplattform 130 aus einem Paarungsmodul 132 und einem Handelsmodulmodul 134 bestehen. Auftragsbücher Modul 136. Das Kopplungsmodul 132 kann so konfiguriert sein, dass es alle Aspekte des Erzeugens und Bereitstellens von vordefinierten Paaren nicht zusammenhängender Wertpapiere für die Auswahl und den Handel durch Händlereinheiten 120 verwaltet. Das Handelsmodulmodul 134 kann so konfiguriert sein, dass es alle Aspekte von Routing - und Anpassungspaar-Handelsaufträgen, die von den Händlerentitäten 120 empfangen werden, verwalten. Das Orderbuchmodul 136 kann so konfiguriert sein, dass es alle Aspekte des Identifizierens und Kommunizierens mit Auftragsbüchern, die den Beinen zugeordnet sind, repräsentiert, die jeden der Wertpapiere repräsentieren, in der von den Händlerentitäten 120 empfangenen Paarbetriebsordnung verwalten. Der Fachmann wird erkennen, dass die Paar-Handelsplattform 130 mit mehr oder weniger Modulen konfiguriert sein kann, um die hier beschriebenen Handelspartner-Verfahren unter Bezugnahme auf 1 und 2 durchzuführen. Wie in den Fig. Wie in den 2 und 3 gezeigt, kann jede der entsprechenden Verfahren 200 und 300 durch eine Verarbeitungslogik ausgeführt werden, die Hardware (z. B. Schaltkreise, dedizierte Logik, programmierbare Logik, Mikrocode, etc.), Software (wie Anweisungen, die auf einer Verarbeitungsvorrichtung laufen) Eine Kombination davon. In einer Ausführungsform können die Verfahren 200 und 300 durch eine oder mehrere Prozessorkomponenten ausgeführt werden, die den Modulen 132 zugeordnet sind. 134 und 136 der Paar-Handelsplattform 130. FEIGE. 2 ist ein Flussdiagramm, das ein Verfahren 200 zum Koppeln von nicht verbundenen Wertpapieren von einer oder mehreren Assetklassen gemäß einer Ausführungsform der Offenbarung veranschaulicht. Bezug nehmend auf Fig. Wie in 2 gezeigt, kann das Verfahren 200 bei Empfang im Schritt 202 initiiert werden. Eine Anforderung, zwei Beine von unabhängigen Wertpapieren aus verschiedenen Assetklassen zu koppeln. Beispielsweise kann eine Anfrage eine Paarung von Apple - (AAPL-) Aktien und Technologieauswahlsektor SPDR (XLK), zwei unabhängige Wertpapiere aus verschiedenen Assetklassen (d. h. ein Eigenkapital und eine ETF) umfassen. In einer anderen Ausführungsform können auch zwei Beine von nicht zusammenhängenden Wertpapieren derselben Assetklasse gepaart werden. Beispielsweise kann eine Anforderung eine Paarung von SPDR Gold Shares (GLD) und SPDR SP 500 (SPY), zwei unabhängige Wertpapiere von einer verwandten Vermögensklasse (d. h. ETFs), umfassen. Bei Empfang einer Anforderung zum Paaren von nicht verbundenen Wertpapieren kann in Schritt 204 eine anfängliche Bestimmung vorgenommen werden. Ob Beine, die für jede der Wertpapiere in der angeforderten Paarung repräsentativ sind, gemeinsam gehandelt werden können. Beispielsweise kann das Paarungsmodul 132 prüfen, ob das Handelsmotormodul 134 konfiguriert ist, um beide Beine der nicht verbundenen Wertpapiere, die in der angeforderten Paarung identifiziert sind, unterzubringen. Wenn in Schritt 204 eine bestätigende Bestimmung erfolgt. Dann kann im Schritt 206 eine zweite Bestimmung vorgenommen werden. Um zu ermitteln, ob ausreichende Liquidität in Verbindung mit jedem der nicht zusammenhängenden Wertpapiere vorhanden ist, um die angeforderte Paarung aufzunehmen. Wenn in Schritt 206 eine positive Bestimmung erfolgt. Dann kann im Schritt 208 eine dritte Bestimmung vorgenommen werden. Ob eine interessante Beziehung (z. B. Kriterien, die die Anforderungsniveaus der Anleger definieren, Handelsmuster zwischen den nicht verbundenen Wertpapieren oder irgendein anderes anwendbares Maß) zwischen jeder der nicht verbundenen Wertpapiere existiert, um die angeforderte Paarung aufzunehmen. Ermittlungen, die sich auf das Vorhandensein einer ausreichenden Liquidität und einer interessanten Beziehung beziehen, können auf marktgetriebenen Daten basieren, die beispielsweise von dem Paarhandelsmodul 130 erhalten werden. Wenn eine bejahende Bestimmung in den Schritten 204 durchgeführt wird. 206 und 208. Dann kann die angeforderte Paarung von unabhängigen Wertpapieren in Schritt 210 erzeugt werden. Und von den Händlereinrichtungen 120 zur Auswahl bereitgestellt. Wenn jedoch eine oder mehrere der in den Schritten 204 durchgeführten Bestimmungen durchgeführt werden. 206 und 208 nicht bestätigt werden, kann das Paarungsmodul 132 so konfiguriert werden, dass es bei Schritt 212 verweigert. Die anfordernde Paarung. FEIGE. 3 ist ein Flussdiagramm, das ein Verfahren 300 zum Handel von Paaren nicht verbundener Wertpapiere aus einer oder mehreren Anlageklassen gemäß einer Ausführungsform der Offenbarung darstellt. Bezug nehmend auf Fig. Wie in 3 gezeigt, kann das Verfahren 300 initiiert werden, wenn in Schritt 302 vorgegeben wird. Vordefinierten Paaren nicht zusammenhängender Wertpapiere aus einer oder mehreren Anlageklassen. Die Auswahl eines vordefinierten Paares kann in Schritt 304 empfangen werden. Zu öffnen, ein Paar Handelsauftrag. Beispielsweise können die Handelsinstanzen 120 aus einer Liste von vordefinierten Paaren nicht zusammenhängender Wertpapiere, die für die Handelsplattform über die Handelsplattform 130 verfügbar sind, suchen und auswählen. Nachdem ein vordefiniertes Paar ausgewählt ist und ein entsprechender Paar-Handelsbefehl geöffnet wird, kann der Handelsauftrag im Schritt 306 weitergeleitet werden. Zu einem Paar Auftragsbuch für Aufträge, die in Verbindung mit dem vordefinierten Paar ausgewählt erhalten werden. Zum Beispiel können die Wertpapiere GLD und SPY als ein vordefiniertes Paar bereitgestellt werden, das als GLDSPY identifiziert ist, und kann bei der Auswahl zu einem Paarauftragsbuch geführt werden, das zum Empfangen von Aufträgen bezüglich GLDSPY vorgesehen ist. Obwohl der Handelsauftrag aus Beinen besteht, die repräsentativ für jeden der zugrundeliegenden Wertpapiere in dem vordefinierten Paar sind, wird er von dem entsprechenden Paarauftragsbuch als Einzelauftrag (d. h. nicht getrennte Bestellungen für jedes Bein in dem Paar) empfangen. Sobald die Paar-Trade-Order in das entsprechende Paar-Orderbuch eingetragen ist, kann dann im Schritt 308 ein Versuch unternommen werden. Die mit jedem Bein der gepaarten Wertpapiere verbunden sind. In einer Ausführungsform kann die Paare-Handelsplattform 130 versuchen, Ordnungsparameter für jedes Bein der gepaarten Wertpapiere unter Verwendung anderer Paar-Handelsaufträge in dem Paarordnungsbuch, das die Auftragsparameter erfüllt, zusammenzubringen. In einer anderen Ausführungsform kann die Paare-Handelsplattform 130 versuchen, Ordnungsparameter durch Auftragsbücher entsprechend der Sicherheit zu vergleichen, die durch jedes Bein in dem Paar dargestellt wird. Eine Bestimmung kann in Schritt 310 vorgenommen werden. Um festzustellen, ob die Auftragsparameter beider Beine erfüllt sind. Wenn und nur dann, wenn die Bestellparameter, die mit jedem Bein der gepaarten Wertpapiere verknüpft sind, erfüllt sind, dann kann die Paar-Trade-Order in Schritt 316 gefüllt werden. Wodurch ein Paarhandelsauftragstransaktion risikolos von einem Ausführungsstandpunkt gemacht wird. Wenn jedoch Auftragsparameter, die mit einem der beiden Paße der gepaarten Wertpapiere assoziiert sind, nicht erfüllt sind, kann im Schritt 312 eine Bestimmung vorgenommen werden. Ob eine Frist für die Durchführung des Paarhandels abgelaufen ist. Wenn die Zeitperiode nicht abgelaufen ist, kann die Paar-Handelsplattform 130 weiterhin versuchen, in Schritt 308 zu versuchen. Passend zum Paarhandelsauftrag. Wenn die Zeitspanne abgelaufen ist und die Paar-Trade-Order nicht gefüllt ist, kann die Paar-Trade-Order in Schritt 314 abgebrochen werden. Es ist anzumerken, daß die in Verbindung mit den Verfahren 200 und 300 beschriebene Abfolge von Vorgängen von den in den entsprechenden Fig. Zum Beispiel können die Operationen bei Schritt 208 vor den Operationen bei Schritt 206 ausgeführt werden. Wie in dem Verfahren 200 von 1 dargestellt. Fig. 4 zeigt eine schematische Darstellung einer Maschine in der beispielhaften Form eines Computersystems 400, in dem ein Satz von Befehlen ausgeführt werden kann, um zu veranlassen, dass die Maschine eine oder mehrere der hier diskutierten Methodologien ausführt. In alternativen Ausführungsformen kann die Maschine mit anderen Maschinen in einem lokalen Netzwerk (LAN), einem Intranet, einem Extranet oder dem Internet verbunden (z. B. vernetzt) sein. Die Maschine kann in der Kapazität eines Servers oder einer Client-Maschine in einer Client-Server-Netzwerkumgebung oder als Peer-Maschine in einer Peer-to-Peer (oder verteilten) Netzwerkumgebung arbeiten. Die Maschine kann ein Personal Computer (PC), ein Tablet PC, eine Set-Top Box (STB), ein Personal Digital Assistant (PDA), ein Mobiltelefon, ein Web-Gerät, ein Server, ein Netzwerk Router, Switch oder Bridge sein , Oder jede Maschine, die in der Lage ist, einen Satz von Befehlen (sequentiell oder anderweitig) auszuführen, die Aktionen festlegen, die von dieser Maschine ausgeführt werden sollen. Während ferner nur eine einzige Maschine dargestellt ist, soll der Begriff Maschine auch jede Sammlung von Maschinen umfassen, die einzeln oder gemeinsam einen Satz (oder mehrere Sätze) von Befehlen ausführen, um eine oder mehrere der hier diskutierten Methoden durchzuführen. Das beispielhafte Computersystem 400 kann aus einer Verarbeitungsvorrichtung 402 bestehen. Einen Festwertspeicher (ROM), einen Flash-Speicher, einen dynamischen Speicher mit wahlfreiem Zugriff (DRAM) (wie z. B. synchroner DRAM (SDRAM) oder Rambus-DRAM (RDRAM) usw.), einen statischen Speicher 406 (z (SRAM), und eine Datenspeichervorrichtung 418, die miteinander über einen Bus 430 kommunizieren. Die Verarbeitungseinrichtung 402 stellt eine oder mehrere Allzweck-Verarbeitungsvorrichtungen, wie etwa einen Mikroprozessor, eine zentrale Verarbeitung dar (CISC) - Mikroprozessor, einen Mikroprozessor mit reduziertem Befehlssatzcomputer (RISC), einen Mikroprozessor mit sehr langem Befehlswort (VLIW) oder einen Prozessor, der andere Befehlssätze oder Prozessoren implementiert, sein Die eine Kombination von Befehlssätzen implementiert. Die Verarbeitungsvorrichtung 402 kann auch eine oder mehrere Spezialverarbeitungsvorrichtungen sein, wie eine anwendungsspezifische integrierte Schaltung (ASIC), ein feldprogrammierbares Gate-Array (FPGA), ein digitales Signalprozessor (DSP), Netzwerk Prozessor oder dergleichen. Die Verarbeitungsvorrichtung 402 ist konfiguriert, um eine Verarbeitungslogik 426 auszuführen, um die Operationen und Schritte durchzuführen, die hierin diskutiert werden. Das Computersystem 400 kann ferner eine Netzwerkschnittstellenvorrichtung 408 umfassen. Das Computersystem 400 kann auch eine Videoanzeigeeinheit 410 (z. B. eine Flüssigkristallanzeige (LCD) oder eine Kathodenstrahlröhre (CRT)), eine alphanumerische Eingabevorrichtung 412 (zB eine Tastatur), eine Cursorsteuervorrichtung 414 (z ) Und eine Signalerzeugungsvorrichtung 416 (z. B. einen Lautsprecher). Die Datenspeichervorrichtung 418 kann ein maschinenlesbares Speichermedium (oder insbesondere ein computerlesbares Speichermedium) 428 mit einem oder mehreren Sätzen von Befehlen (z. B. Software 422) umfassen, die irgendeines oder mehrere der hierin beschriebenen Verfahrensweisen von Funktionen verkörpern. Beispielsweise kann die Software 422 Anweisungen speichern, um einen Cash-Equities-Paarenhandel durchzuführen. Die Software 422 kann sich auch vollständig oder zumindest teilweise innerhalb des Hauptspeichers 404 und innerhalb der Verarbeitungsvorrichtung 402 befinden, während der Ausführung davon durch den Hauptspeicher 404 des Computersystems 400 und die Verarbeitungsvorrichtung 402 ebenfalls maschinenlesbare Speichermedien bilden. Die Software 422 kann ferner über die Netzwerkschnittstelleneinrichtung 408 über ein Netzwerk 420 übertragen oder empfangen werden. Das maschinenlesbare Speichermedium 428 kann auch verwendet werden, um Anweisungen zur Durchführung eines Cash-Equity-Paarenhandels zu speichern. Während das maschinenlesbare Speichermedium 428 in einem exemplarischen Ausführungsbeispiel als ein einzelnes Medium gezeigt ist, sollte der Ausdruck maschinenlesbares Speichermedium dazu verwendet werden, ein einzelnes Medium oder mehrere Medien (z. B. eine zentrale oder verteilte Datenbank und oder zugehörige Caches und Server) einzuschließen ), Die den einen oder die mehreren Sätze von Befehlen speichern. Der Ausdruck maschinenlesbares Speichermedium soll auch jedes Medium umfassen, das in der Lage ist, einen Satz von Anweisungen für die Ausführung durch die Maschine zu speichern oder zu kodieren, und der bewirkt, dass die Maschine eine oder mehrere der Methoden der vorliegenden Offenbarung ausführt. Der Ausdruck maschinenlesbares Speichermedium soll dementsprechend auf Festkörper-Speicher und optische und magnetische Medien beschränkt sein, ohne darauf beschränkt zu sein. Während viele Änderungen und Modifikationen der vorliegenden Offenbarung dem Fachmann nach dem Lesen der vorstehenden Beschreibung zweifellos offensichtlich werden, ist es selbstverständlich, daß jede spezielle, als Beispiel dargestellte und dargestellte Ausführungsform keineswegs ist Als beschränkend angesehen werden. Daher beabsichtigen Verweise auf Einzelheiten der verschiedenen Ausführungsformen nicht, den Umfang der Ansprüche einzuschränken, die an sich nur jene Merkmale rezitieren, die als die Offenbarung angesehen werden. Ruggiero, Murray A. Jr. Equity Futures: Trades Site in diesem kühnen neuen Markt Futures v30 N1 Seiten 58-61 Sep. 2001. Financial Times Japan ed. Spinnen und Viper finden favourin die Equity-Dschungel Abschnitt: Global Investment Fund Managemen 7. April 2002. Spiro, L. et al. Es war nicht gerade der Anleihemarkt, den LTCM gefährdet, Geschäft Woche, 9. November 1998, Nr. 3603, p. GIB gewinnt den European Hedge Fund Award, Emerging Markets Daftafile, Bahrain Tribune, 12.06.2001. Chernoff, Hedge-Fonds-Strategien können Zeitbomben sein Kurze Tenures neigen dazu, Sharpes, Investment News aufzublasen, S. 24Mai 14, 2001. M. OBrien, Brent Nyitray und Daniel Morgan Join Bear Stearns Relative Value Desk, Business Wire, 25. Januar 2001 M. Fischer, Konservativer, wertorientierter Ansatz zur Vermögensallokation, MARHedge, Fondsübersicht Nr. 76 S. 22, April 2000. A. Capon, Jenseits des Preisimperativs, International Securities Lending, Viertes Quartal 1999, pp. 12-22 ISSN: 09649301, Viertes Viertel 1999. J. Ogden, HSBC gesetzt, zum der alternativen Spur zu brennen, um Anlage zu finanzieren HSBC hedges Wetten in neuer Tendenz, Südchina-Morgen-Pfosten, Sonntag-Geld pp. 10, 11. Juli 1999. L. Spiro et al. H. Rossman, Alternative Strategien: Risiken, Belohnungen und Erwägungen, Trusts Estates, vol. H. Rossman, Hrsg. 134n5, S. 32-40, Mai 1995. J. Newman, Long and Short of CFD (Verträge über die Differenz), Money Marketing, Bd. 64, 9. November 2000. M. Garvey et al. Wie Makler den Handel für langfristige Kunden in wettbewerbsfähigen Wertpapiermärkten erleichtern. Zeitschrift für anorganische und allgemeine Chemie. 68, n1, p1 (33), Jan. 1995. Kanadisches Quantex Benutzerhandbuch, RBC Dominion Securities Inc. vol. 1: Trade Execution, 1992. Intl-Recherchenbericht für PCTUS0237922 vom 27. März 2003. Rechtsanwalt, Agent oder Unternehmen: Clifford Chance US LLP-Eltern-Falldaten: CROSS-REFERENCE TO VERWANDTE ANMELDUNG Diese Anmeldung beansprucht den Vorteil des Anmeldetags von US Vorläufige Anwendung Ser. Nr. 60334,163 mit dem Titel Verfahren und System für Handelspaare von Wertpapieren, das am 29. November 2001 eingereicht wurde und deren Inhalt durch Bezugnahme hierin aufgenommen wird. Verfahren nach einem der Ansprüche 1 bis 4, dadurch gekennzeichnet, dass die Datenpakete (1, 2, 3, Eine erste Sicherheit, eine Anfrage zum Handel einer zweiten Sicherheit und eine Anfrage zum Handel der ersten Sicherheit und der zweiten Sicherheit mit einer minimalen Spreizbegrenzung zu handeln, und wobei die erste Sicherheit und die zweite Sicherheit jeweils einen Gebotspreis und einen Briefpreis aufweisen Bestimmen der Bidbidspreizung auf dem Markt der ersten Sicherheit und der zweiten Sicherheit, welche die auf dem Markt der ersten Sicherheit verbreitete Askask-Verbreitung bestimmt, und wobei die zweite Sicherheit bestimmt, daß die minimale Spreizgrenze jeder Paarhandelsanforderung durch einen Bereich der Bidbidspreizung erfüllt ist Und wobei die Askask-Spreizung eine Transaktion zwischen einem ersten Abschnitt des Handels der ersten Sicherheit in der einen Paar-Handelsanforderung und mindestens einer Nicht-Paar-Handelsanforderung ausführt, vorausgesetzt, dass die minimale Spreizgrenze der einen Paar-Handelsanforderung durch das erfüllt wird Bereich des besagten Bidbidspreads und besagter Askask unter Verwendung eines Computers einen zweiten Teil des besagten Handels der besagten ersten Sicherheit in der besagten einen Paar-Handelsanforderung und wenigstens einen ersten Teil des Handels der besagten zweiten Sicherheit in dem besagten einen Paar-Handel verbreitet und anpaßt Wenn ein Bereich der minimalen Spreizgrenze der einen Paar-Handelsanforderung und der anderen Paar-Handelsanforderung mit dem Bereich der Bidbid-Verbreitung und der Askask-Verbreitung überlappt. 2. Verfahren nach Anspruch 1, wobei der Schritt des Ausführens einer Transaktion für den ersten Abschnitt des Handels der ersten Sicherheit in der einen Paar-Handelsanfrage den Schritt umfasst: Ausführen einer Transaktion für den ersten Teil des Handels des ersten Sicherheit in der einen Paar Handel Anfrage in einem externen Markt. Verfahren nach Anspruch 1, wobei der Schritt des Ausführens einer Transaktion von einem Finanzinstitut durchgeführt wird, das einen Auftragsbestand hat und der Schritt des Ausführens einer Transaktion den Schritt umfasst: Ausführen einer Transaktion für den ersten Teil des Handels des ersten Sicherheit in der einen Paar-Handelsanfrage gegen den bestellten Auftragsbestand. 4. Verfahren nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, dass eine Transaktion zwischen einem zweiten Abschnitt des Handels der zweiten Sicherheit in der einen Paar-Handelsanforderung und mindestens einer anderen Nichtpaar-Handelsanforderung ausgeführt wird, vorausgesetzt, dass die minimale Spreizgrenze der einen Paar-Handelsanforderung durch den Bereich der Bidbidspreizung und der Askaskspreizung erfüllt ist, und wobei der Schritt des Ausführens des ersten Teils der Ein-Paar-Handelsanforderung und des Ausführens des zweiten Teils der Ein-Paar-Handelsanforderung die folgenden Schritte umfasst: Bestimmen, ob Der Gebotspreis des ersten Wertpapiers und der Geldkurs des zweiten Wertpapiers einem Spread-Limit entsprechen, das einen Betrag des zweiten Wertpapiers, der verkauft werden kann, basierend auf einer Gebotsgröße, die dem zweiten Wert zugeordnet ist, eine äquivalente Menge des ersten Wertpapiers, Basierend auf dem Betrag der zweiten Sicherheit, die verkauft werden kann, anzupassen, wobei der äquivalente Betrag der ersten Sicherheit auf der Basis von Anpassungskriterien berechnet wird, die einen Kaufpreis für den angepaßten äquivalenten Betrag der ersten Sicherheit auf der Grundlage der Spreizgrenze berechnen, die eine einleitende Bestellung ausführt Des bereinigten äquivalenten Betrags der ersten Sicherheit zum Kaufpreis und zum Ausführen eines Deckungsauftrags, um den Betrag der zweiten Sicherheit zu verkaufen. 5. Verfahren nach einem der Ansprüche 1 bis 4, dadurch gekennzeichnet, dass der Schritt des Ausführens eines Kaufvertrags umfasst: Ausführen eines Deckungsauftrags, um den Betrag des zweiten Wertpapiers zum Kaufpreis des zweiten Wertpapiers zu verkaufen. 6. Verfahren nach einem der Ansprüche 1 bis 4, dadurch gekennzeichnet, dass der Preis des ersten Wertpapiers und des Briefkurses des zweiten Wertpapiers einem Spread-Limit entsprechen, das einen Betrag des ersten Wertpapiers ermittelt, das auf Basis eines Angebots gekauft werden kann Die mit der ersten Sicherheit assoziiert ist, eine äquivalente Menge der zweiten Sicherheit zu berechnen, die auf der Grundlage des Betrags der zweiten Sicherheit verkauft werden kann, die gekauft werden kann, indem die äquivalente Menge der zweiten Sicherheit auf der Grundlage von Anpassungskriterien, die einen Verkaufspreis für das eingestellte Äquivalent berechnen, angepasst wird Betrag der zweiten Sicherheit auf der Grundlage der Spreizbegrenzung, die eine auslösende Anweisung ausführt, um den bereinigten äquivalenten Betrag der zweiten Sicherheit zu dem Verkaufspreis zu verkaufen und einen Deckungsauftrag auszuführen, um den Betrag der ersten Sicherheit zu erwerben. 7. Verfahren nach einem der Ansprüche 1 bis 6, dadurch gekennzeichnet, dass der Schritt zum Ausführen eines Kaufauftrags umfasst: Ausführen eines Deckungsauftrags, um den Betrag des ersten Wertpapiers zum Kaufpreis des ersten Wertpapiers zu erwerben. 8. Verfahren nach Anspruch 6, dadurch gekennzeichnet, dass die Einstellkriterien eine Mindestmenge und eine Höchstmenge umfassen. 9. Verfahren nach Anspruch 8, dadurch gekennzeichnet, dass der Schritt des Ausführens eines Initiierungsbefehls den folgenden Schritt umfasst: Runden des Initiierungsbefehls zu einer runden Losgröße. Verfahren nach Anspruch 1, wobei der Schritt des Ausführens eines ersten Teils des Handels der ersten Sicherheit in der einen Paar Handelsanfrage den Schritt umfasst: Ausführen eines ersten Teils des Handels der ersten Sicherheit in dem einen Paar Handel Anforderung in einer Vielzahl von Tranchen. 11. The method of claim 1, wherein said one pair trade request has a first spread limit and said another pair trade request has a second spread limit and wherein said step of matching said second portion of said trade of said first security in said one pair trade request and at least a first portion of the trade of said second security in said one pair trade request against said another pair trade request further includes the steps of: determining that a range of said first spread limit and said second spread limit overlaps with a market spread setting a spread level calculating prices for the first security and the second security that are within the market spread and based on said spread level and matching said second portion of said trade of said first security in said one pair trade request and at least a first portion of the trade of said second security in said one pair trade request against said another pair trade request based on said calculated prices. 12. The method of claim 11, wherein the step of setting a spread level includes the steps of: calculating a mean between said first spread limit and said second spread limit and setting said spread level as said mean if said mean is within said market spread. 13. The method of claim 12, further including the step of: identifying a spread amount that is closest to said mean and within said market spread and setting said spread level as said spread amount if said mean is not within said market spread. 14. The method of claim 1, wherein said one pair trade request has a first spread limit, a buy ratio and a sell ratio, said another pair trade request has a second spread limit, a buy ratio and a sell ratio and wherein the step of matching a second portion of said trade of said first security in said one pair trade request and at least said first portion of the trade of said second security in said one pair trade request against said another pair trade request further includes the steps of: determining that said buy ratio and said sell ratio associated with said one trade request does not equal said buy ratio and said sell ratio of said another pair trade request and that an overlap exists between the range of said first spread limit and said second spread limit and a market spread determining that market prices exist that are within the overlap determining a mismatch amount in said second security based on a difference between said buy ratio and said sell ratio associated with said one pair trade request and said buy ratio and said sell ratio of said another pair trade request calculating a cross amount for said first security and said second security selecting a crossing price for said first security and said second security that is within said overlap determining that said mismatch amount is available at said crossing price for said second security matching said second portion of said trade of said first security in said one pair trade request and at least said first portion of the trade of said second security in said one pair trade request against said another pair trade request based on said selected prices and executing a transaction for said mismatch amount of said second security at said crossing price for said second security. 15. The method of claim 14, wherein the step of determining that said mismatch amount is available at said crossing price for said second security includes the step of: determining that said mismatch amount is available in an external market at said crossing price for said second security. 16. The method of claim 14, wherein the step of determining that said mismatch amount is available is performed by a financial institution having an order inventory and the step of determining that said mismatch amount is available at said crossing price for said second security includes the step of: determining that said mismatch amount is available in said order inventory at said crossing price for said second security. 17. The method of claim 1, wherein said one pair trade request and said another pair trade request indicate a number of spreads and wherein the step of matching a second portion of said trade of said first security in said one pair trade request and at least said first portion of the trade of said second security in said one pair trade request against said another pair trade request, includes the step of: matching a second portion of said trade of said first security in said one pair trade request and at least said first portion of the trade of said second security in said one pair trade request against said another pair trade request if said number of spreads is greater than a minimum number of spreads. 18. The method of claim 1, including the step of: receiving a preference for filling at least some of said plurality of trade requests via said executing step. 19. The method of claim 1, including the step of: receiving a preference for filling at least some of said plurality of trade requests via said matching step. 20. The method of claim 1, wherein a client submits a query regarding a status of said pair trade request and the status of said pair trade request is continuously updated in real time. 21. The method of claim 19, wherein said preference is submitted by a client electronically. 22. The method of claim 1, wherein a client receives a simultaneous report when said pair trade request is filled and the client confirms said pair trade electronically. 23. The method of claim 1, further comprising: executing a transaction between a second portion of the trade of said second security in said one pair trade request and at least another non-pair trade request, provided that the minimum spread limit of said one pair trade request is met by said range of said bidbid spread and said askask spread, and wherein the step of executing said first portion of said one pair trade request and executing said second portion of said one pair trade request includes the step of: determining whether the ask price of the first security and the ask price of the second security meet a spread limit determining an amount of the second security that can be bought based on an ask size associated with the second security calculating an equivalent amount of said first security that can be sold based on the amount of the second security that can be bought adjusting said equivalent amount of said first security based on adjustment criteria calculating a selling price for said adjusted equivalent amount of said first security based on the spread limit executing an initiating order to sell said adjusted equivalent amount of said first security at said selling price and executing a covering order to purchase said amount of said second security. 24. A system for fulfilling a pair trade request, said system receiving a plurality of pair trade requests, comprising one pair trade request and another pair trade request, wherein each pair trade request comprises a request to trade a first security, a request to trade a second security, and a request to trade said first security and said second security with a minimum spread limit, and wherein said first security and said second security each have a bid price and an ask price, comprising: a pair trading engine for: determining the bidbid spread in the market of said first security and said second security determining the askask spread in the market of said first security and said second security determining that the minimum spread limit of each pair trade request is met by a range of said bidbid spread and said askask spread for every security executing a transaction between a first portion of the trade of said first security in said one pair trade request and at least one non-pair trade request, provided that the minimum spread limit of said one pair trade request is met by said range of said bidbid spread and said askask spread and a pair crossing network for matching a second portion of said trade of said first security in said one pair trade request and at least a first portion of the trade of said second security in said one pair trade request against said another pair trade request, provided that a range of the minimum spread limit of said one pair trade request and said another pair trade request overlaps with said range of said bidbid spread and said askask spread. 25. The system of claim 24, further comprising a link to an external market wherein said pair trading engine forwards said transaction for said first portion of the trade of said first security in said one pair trade request for execution in said external market via said link. 26. The system of claim 24, further comprising a financial institution having an order inventory and wherein said pair trading engine executes said transaction for said first portion of the trade of said first security in said one pair trade request against said order inventory. 27. The system of claim 24, wherein said pair trading engine determines whether the bid price of the first security in said one pair trade request and the bid price of the second security in said one pair trade request meet a spread limit determines an amount of the second security that can be sold based on a bid size associated with the second security calculates an equivalent amount of said first security that can be bought based on the amount of said second security that can be sold adjusts said equivalent amount of said first security based on adjustment criteria calculates a purchase price for said adjusted equivalent amount of said first security based on the spread limit executes an initiating order to buy said adjusted equivalent amount of said first security at said purchase price and executes a covering order to sell said amount of the second security. 28. The system of claim 27, wherein the pair trading engine executes a covering order to sell said amount of the second security at the bid price of the second security. 29. The system of claim 27, wherein the pair trading engine determines whether the ask price of the first security and the ask price of the second security meet a spread limit determines an amount of the first security that can be bought based on an offer size associated with the first security calculates an equivalent amount of said second security that can be sold based on the amount of the second security that can be bought adjusts said equivalent amount of said second security based on adjustment criteria calculates a selling price for said adjusted equivalent amount of said second security based on the spread limit executes an initiating order to sell said adjusted equivalent amount of said second security at said selling price and executes a covering order to purchase said amount of the first security. 30. The system of claim 29, wherein the pair trading engine executes a covering order to purchase said amount of the first security at the ask price of the first security. 31. The system of claim 27, wherein said adjustment criteria include a minimum amount and a maximum amount. 32. The system of claim 31, wherein the pair trading engine rounds said initiating order to a round lot size. 33. The system of claim 24, wherein the pair trading engine executes at least a portion of the trade of one of said securities in one of said pair trade requests in a plurality of tranches. 34. The system of claim 24, wherein said one pair trade request has a first spread limit and said another pair trade request has a second spread limit and wherein the pair crossing network determines that a range of said first spread limit and said second spread limit overlaps with a market spread sets a spread level calculates prices for the first security and the second security that are within the market spread and based on said spread level and matches said second portion of said trade of said first security in said one pair trade request and at least a first portion of the trade of said second security in said one pair trade request against another of said plurality of pair trade request based on said calculated prices. 35. The system of claim 34, wherein the pair crossing network calculates a mean between said first spread limit and said second spread limit and sets said spread level as said mean if said mean is within said market spread. 36. The system of claim 35, wherein the pair crossing network identifies a spread amount that is closest to said mean and within said market spread and sets said spread level as said spread amount if said mean is not within said market spread. 37. The system of claim 24, wherein said one pair trade request has a first spread limit, a buy ratio and a sell ratio, said another pair trade request has a second spread limit, a buy ratio and a sell ratio and wherein the pair crossing network determines that said buy ratio and said sell ratio associated with said one pair trade request does not equal said buy ratio and said sell ratio of said another pair trade request and that an overlap exists between the range of said first spread limit and said second spread limit and a market spread determines that market prices exist that are within the overlap determines a mismatch amount in said second security based on a difference between said buy ratio and said sell ratio associated with said one pair trade request and said buy ratio and said sell ratio of said another pair trade request calculates a cross amount for said first security and said second security selects a crossing price for said first security and said second security that is within said overlap determines that said mismatch amount is available at said crossing price for said second security matches said second portion of said trade of said first security in said one pair trade request and at least said first portion of the trade of said second security in said one pair trade request against said another pair trade request based on said selected prices and executes a transaction for said mismatch amount of said second security at said crossing price for said second security. 38. The system of claim 37, wherein the pair crossing network determines that said mismatch amount is available in an external market at said crossing price for said second security. 39. The system of claim 37, wherein the pair crossing network determines that said mismatch amount is available at said crossing price for said second security in said an order inventory of a financial institution. 40. The system of claim 24, wherein said one pair trade request and said another pair trade request indicate a number of spreads and wherein the pair crossing network matches said second portion of said trade of said first security in said one pair trade request and at least said first portion of the trade of said second security in said one pair trade request against said another pair trade request if said number of spreads is greater than a minimum number of spreads. 41. The system of claim 24, wherein said plurality of pair trade requests include at least some pair trade requests indicating a preference for execution via said pair crossing network, said system further comprising a portfolio manager in communications with said pair crossing network, said portfolio manager receiving said plurality of pair trade requests and routing said at least some of said plurality of trade requests to said pair crossing network according to said preference. 42. The system of claim 24, said system further comprising a pair trading engine for executing at least some of said plurality of pair trade requests, said system further comprising a portfolio manager in communications with said pair trading engine, wherein said plurality of pair trade requests include at least some pair trade requests indicating a preference for execution via said pair trading engine, said portfolio manager receiving said plurality of pair trade requests and routing said at least some of said plurality of trade requests to said pair trading engine according to said preference. 43. The method of claim 24, wherein a client submits a query regarding a status of said pair trade request and the status of said pair trade request is continuously updated in real time. 44. The method of claim 41, wherein said preference is submitted by a client electronically. 45. The method of claim 24, wherein a client receives a simultaneous report when said pair trade request is filled and the client confirms said pair trade electronically. 46. A computer readable storage medium storing instructions for fulfilling a pair trade request that, when executed by a computer, cause to computer to: receive a plurality of pair trade requests, comprising one pair trade request and another pair trade request, wherein each pair trade request comprises a request to trade a first security, a request to trade a second security, and a request to trade said first security and said second security with a minimum spread limit, and wherein said first security and said second security each have a bid price and an ask price determine the bidbid spread in the market of said first security and said second security determine the askask spread in the market of said first security and said second security determine that the minimum spread limit of each pair trade request is met by a range of said bidbid spread and said askask spread execute a transaction between a first portion of the trade of said first security in said one pair trade request and at least one non-pair trade request, provided that the minimum spread limit of said one pair trade request is met by the range of said bidbid spread and said askask spread and match a second portion of said trade of said first security in said one pair trade request and at least a first portion of the trade of said second security in said one pair trade request against said another pair trade request, provided that a range of the minimum spread limit of said one pair trade request and said another pair trade request overlaps with said range of said bidbid spread and said askask spread. BACKGROUND The following invention relates to a system and method for trading securities and, in particular, for a system and method of trading securities in pairs. A recognized strategy for trading securities is known as pair-trading. Pair-trading is a non-directional investment strategy in which the investor identifies two securities having similar characteristics and the securities are currently trading at a price relationship that is out of their historical trading range. The investor exploits the price relationship between the securities by buying the undervalued security while short-selling the overvalued security. Because pair-trading is a market-neutral strategy, it is a particularly desirable strategy for investing in volatile markets. One context in which pair trading is useful is where an investor desires to take advantage of an arbitrage opportunity resulting from a merger between two companies. For example, Company A has announced a definitive agreement to acquire Company T in which case Company T shareholders will receive 0.5 shares of Company A stock for each share of Company T stock they own. The investor desires to capture the spread between the offered consideration (0.5 shares of A) and the price of T stock. To do this, the investor buys shares in T stock and sells shares of A stock. For instance, if stock T is trading at 28 per share and stock A is trading at 60 per share, then the investor may execute a trade for 200,000 spreads by buying 200,000 shares of T stock and selling 100,000 shares of A stock. After the merger takes place, the investor will cover the short position in stock A with the 100,000 shares of A stock the investors receives in exchange of the 200,000 shares the investor held of stock T. Thus, by executing the pair trade, the investor locks in a 400,000 profit (assuming that the merger goes through). The process of executing a pair trade thus includes executing individual trades directed to each leg of the pair trade request. An example of a system for executing trades for filling a pair trade request is the Quantex system from ITG (itgincproductsquantexquantex. html) of 380 Madison Avenue New York, N. Y. 10017. A challenge in implementing a pair trade is to find a counterparty for a particular position an investor desires to establish while minimizing leg risk. Typically, a large pair trade is performed off the market as a private transaction negotiated by a financial institution that services large clients. For example, if an investor desires to execute a pair trade betting that a proposed merger between two companies will go through, the investor would approach a financial institution seeking an investor that is willing to bet against the merger. The financial institution then acts as an intermediary between the two investors in which the investors establish equal and opposite positions in the stock of the proposed merger partners thereby completing the pair trade. Thus by matching two pair trade requests so that the transactions associated with each of the pair trade legs are executed simultaneously, neither investor is exposed to leg risk that would otherwise result for the period of time between execution of the first leg and the second leg of the pair trade. There are numerous drawbacks associated with the prevalent pair-trading practice. First, pair-trading is typically limited to clients of large financial institutions that have the ability to identify suitable counterparties for a particular pair trade. This is especially the case when the pair trade involves a large amount of stock or illiquid stocks in which the only way to execute the trade and minimize leg risk is via an off the market transaction negotiated by a financial institution. Also, because a pair-trade is typically negotiated by the parties with a financial institution as an intermediary, the process is often slow and inefficient. Furthermore, pair-trading under current practice is generally best suited for large clients seeking to establish large positions thereby providing the financial institutions with the economic incentive to execute the transaction. Smaller clients, however, must rely on the markets for executing pair trades, which is unsuitable for illiquid stocks and also results in increased leg risk. Accordingly, it is desirable to provide a system and method for trading securities in pairs. SUMMARY OF THE INVENTION The present invention is directed to overcoming the drawbacks of the prior art pair trading practices. Under the present invention a method is provided for fulfilling a pair trade request and includes the steps of receiving a plurality of pair trade requests executing a transaction for a first portion of one of the plurality of pair trade requests and matching a second portion of the one of the plurality of pair trade requests against another of the plurality of pair trade requests. In an exemplary embodiment, the method includes the step of executing a transaction for a first portion of one of the plurality of pair trade requests in an external market. In another exemplary embodiment, the method includes the step of executing a transaction for a first portion of one of the plurality of pair trade requests against the order inventory. In yet another exemplary embodiment, the pair trade request includes a first security having a bid price and an ask price and a second security having a bid price and an ask price, and the method includes the steps of determining whether the bid price of the first security and the bid price of the second security meet a spread limit determining an amount of the second security that can be sold based on a bid size associated with the second security calculating an equivalent amount of the first security that can be bought based on the amount of the second security that can be sold adjusting the equivalent amount of the first security based on adjustment criteria calculating a purchase price for the adjusted equivalent amount of the first security based on the spread limit executing an initiating order to buy the adjusted equivalent amount of the first security at the purchase price and executing a covering order to sell the amount of the second security. In still yet another exemplary embodiment, the method includes the step of executing a covering order to sell the amount of the second security at the bid price of the second security. In an exemplary embodiment, the method includes the steps of determining whether the ask price of the first security and the ask price of the second security andor the bid price of the first security and the bid price of the second security meet a spread limit determining an amount of the first security that can be bought based on an offer size associated with the first security calculating an equivalent amount of the second security that can be sold based on the amount of the second security that can be bought adjusting the equivalent amount of the second security based on adjustment criteria calculating a selling price for the adjusted equivalent amount of the second security based on the spread limit executing an initiating order to sell the adjusted equivalent amount of the second security at the selling price and executing a covering order to purchase the amount of the first security. In another exemplary embodiment, the method includes the step of executing a covering order to purchase the amount of the first security at the ask price of the first security. In yet another exemplary embodiment, the adjustment criteria include a minimum amount and a maximum amount. In still yet another exemplary embodiment, the method includes the step of rounding the initiating order to a round lot size. In an exemplary embodiment, the method includes the step of executing a first portion of one of the plurality of pair trade requests in a plurality of tranches. In another exemplary embodiment, the one of the plurality of pair trade requests and the another of the plurality of pair trade requests include a first security and a second security, the one of the plurality of pair trade requests has a first spread limit and the another of said plurality of trade requests has a second spread limit and wherein the method includes the steps of determining that a range of the first spread limit and the second spread limit overlaps with a market spread setting a spread level calculating prices for the first security and the second security that are within the market spread and based on the spread level and matching the second portion of the one of the plurality of pair trade requests against another of the plurality of pair trade requests based on the calculated prices. In yet another exemplary embodiment, the method includes the steps of calculating a mean between the first spread limit and the second spread limit and setting the spread level as the mean if the mean is within the market spread. In still yet another exemplary embodiment, the method includes the step of identifying a spread amount that is closest to the mean and within the market spread and setting the spread level as the spread amount if the mean is not within the market spread. In an exemplary embodiment, the one of the plurality of pair trade requests and the another of the plurality of pair trade requests include a first security and a second security, the one of the plurality of pair trade requests has a first spread limit, a buy ratio and a sell ratio, the another of the plurality of trade requests has a second spread limit, a buy ratio and a sell ratio and the method includes the steps of determining that the buy ratio and the sell ratio associated with the one of the plurality of trade requests does not equal the buy ratio and the sell ratio of the another of the plurality of trade requests and that an overlap exists between range of the first spread limit and the second spread limit and a market spread determining that market prices exist that are within the overlap determining a mismatch amount in the second security based on a difference between the buy ratio and the sell ratio associated with the one of the plurality of trade requests and the buy ratio and the sell ratio of the another of the plurality of trade requests calculating a cross amount for the first security and the second security selecting a crossing price for the first security and the second security that is within the overlap determining that the mismatch amount is available at the crossing price for the second security matching the second portion of the one of the plurality of pair trade requests against another of the plurality of pair trade requests based on the calculated prices and executing a transaction for the mismatch amount of the second security at the crossing price for the second security. In another exemplary embodiment, the method includes the step of determining that the mismatch amount is available in an external market at the crossing price for the second security. In yet another exemplary embodiment, the method is performed by a financial institution having order inventory and includes the step of determining that the mismatch amount is available in the order inventory at the crossing price for the second security. In still yet another exemplary embodiment, the one of the plurality of pair trade requests and the another of the plurality of pair trade requests indicate a number of spreads and the method includes the step of matching a second portion of the one of the plurality of pair trade requests against another of the plurality of pair trade requests if the number of spreads is greater than a minimum number of spreads. In an exemplary embodiment, the method includes the step of receiving a preference for filling at least some of the plurality of trade requests via the step of executing a transaction for a first portion of one of the plurality of pair trade requests, described above. In another exemplary embodiment, the method includes the step of receiving a preference for filling at least some of the plurality of trade requests via the step of matching a second portion of the one of the plurality of pair trade requests against another of the plurality of pair trade requests, described above. Under the present invention, a method for fulfilling a pair trade request is provided and includes the steps of receiving a plurality of pair trade requests and matching at least a portion of one of the plurality of pair trade requests against another of the plurality of pair trade requests. Under the present invention, a system for fulfilling a pair trade request is provided, the system receiving a plurality of pair trade requests and includes a pair trading engine for executing a transaction for a first portion of one of the plurality of pair trade requests. The system also includes a pair crossing network for matching a second portion of said one of the plurality of pair trade requests against another of the plurality of pair trade requests. In an exemplary embodiment, the system includes a link to external markets and wherein the pair trading engine executes the transaction for the first portion of one of the plurality of pair trade requests in the external markets. In another exemplary embodiment, the system includes a financial institution having an order inventory and wherein the pair trading engine executes the transaction for the first portion of one of the plurality of pair trade requests against the order inventory. In yet another exemplary embodiment, the pair trade request includes a first security having a bid price and an ask price and a second security having a bid price and an ask price, and wherein the pair trading engine determines whether the bid price of the first security and the bid price of the second security meet a spread limit determines an amount of the second security that can be sold based on a bid size associated with the second security calculates an equivalent amount of the first security that can be bought based on the amount of the second security that can be sold adjusts the equivalent amount of the first security based on adjustment criteria calculates a purchase price for the adjusted equivalent amount of the first security based on the spread limit executes an initiating order to buy said adjusted equivalent amount of the first security at the purchase price and executes a covering order to sell the amount of the second security. In still yet another exemplary embodiment, the pair trading engine executes a covering order to sell the amount of the second security at the bid price of the second security. In an exemplary embodiment, the pair trading engine determines whether the ask price of the first security and the ask price of the second security meet a spread limit determines an amount of the first security that can be bought based on an offer size associated with the first security calculates an equivalent amount of the second security that can be sold based on the amount of the second security that can be bought adjusts said equivalent amount of the second security based on adjustment criteria calculates a selling price for the adjusted equivalent amount of the second security based on the spread limit executes an initiating order to sell the adjusted equivalent amount of the second security at the selling price and executes a covering order to purchase the amount of the first security. In another exemplary embodiment, the pair trading engine executes a covering order to purchase the amount of the first security at the ask price of the first security. In yet another exemplary embodiment, the pair trading engine rounds the initiating order to a round lot size. In still yet another exemplary embodiment, the pair trading engine executes a first portion of one of the plurality of pair trade requests in a plurality of tranches. In an exemplary embodiment, the one of the plurality of pair trade requests and the another of the plurality of pair trade requests include a first security and a second security, the one of the plurality of pair trade requests has a first spread limit and the another of the plurality of trade requests has a second spread limit and wherein the pair crossing network determines that a range of the first spread limit and the second spread limit overlaps with a market spread sets a spread level calculates prices for the first security and the second security that are within the market spread and based on the spread level and matches the second portion of said one of the plurality of pair trade requests against another of the plurality of pair trade requests based on the calculated prices. In another exemplary embodiment, the pair crossing network calculates a mean between the first spread limit and the second spread limit and sets the spread level as the mean if the mean is within the market spread. In yet another exemplary embodiment, the pair crossing network identifies a spread amount that is closest to the mean and within the market spread and sets the spread level as the spread amount if the mean is not within the market spread. In still yet another exemplary embodiment, the one of said plurality of pair trade requests and the another of the plurality of pair trade requests include a first security and a second security, the one of the plurality of pair trade requests has a first spread limit, a buy ratio and a sell ratio, the another of the plurality of trade requests has a second spread limit, a buy ratio and a sell ratio and wherein the pair crossing network determines that the buy ratio and the sell ratio associated with the one of the plurality of trade requests does not equal the buy ratio and the sell ratio of the another of the plurality of trade requests and that an overlap exists between range of the first spread limit and the second spread limit and a market spread determines that market prices exist that are within the overlap determines a mismatch amount in the second security based on a difference between the buy ratio and the sell ratio associated with the one of the plurality of trade requests and the buy ratio and the sell ratio of the another of the plurality of trade requests calculates a cross amount for the first security and the second security selects a crossing price for the first security and the second security that is within said overlap determines that the mismatch amount is available at the crossing price for the second security matches the second portion of the one of the plurality of pair trade requests against another of the plurality of pair trade requests based on the calculated prices and executes a transaction for the mismatch amount of the second security at the crossing price for the second security. In an exemplary embodiment, the pair crossing network determines that the mismatch amount is available in an external market at the crossing price for the second security. In another exemplary embodiment, the pair crossing network determines that the mismatch amount is available in the order inventory at the crossing price for the second security. In yet another exemplary embodiment, the one of said plurality of pair trade requests and the another of the plurality of pair trade requests indicate a number of spreads and wherein the pair crossing network matches a second portion of the one of the plurality of pair trade requests against another of the plurality of pair trade requests if the number of spreads is greater than a minimum number of spreads. In still yet another exemplary embodiment, the plurality of pair trade requests include at least some pair trade requests indicating a preference for execution via said pair crossing network, and the system further includes a portfolio manager in communications with the pair crossing network, the portfolio manager receiving the plurality of pair trade requests and routing the at least some pair trade requests to the pair crossing network according to the preference. In an exemplary embodiment, the system includes a pair trading engine for executing at least some of the plurality of pair trade requests, further includes a portfolio manager in communications with the pair trading engine and wherein the plurality of pair trade requests include at least some pair trade requests indicating a preference for execution via the pair trading engine, the portfolio manager receiving the plurality of pair trade requests and routing the at least some of the plurality of trade requests to the pair trading engine according to the preference. Under the present invention, a system for fulfilling a pair trade request is provided, wherein the system receives a plurality of pair trade requests and includes a pair crossing network for matching at least one of the plurality of pair trade requests against another of the plurality of pair trade requests. Accordingly, a method and a system are provided for trading pair securities. The invention accordingly comprises the features of construction, combination of elements and arrangement of parts that will be exemplified in the following detailed disclosure, and the scope of the invention will be indicated in the claims. Other features and advantages of the invention will be apparent from the description, the drawings and the claims. DESCRIPTION OF THE DRAWINGS For a fuller understanding of the invention, reference is made to the following description taken in conjunction with the accompanying drawings, in which: FIG. 1 is a block diagram of a system for trading securities in pairs according to the present invention FIG. 2 is a flowchart of the steps a pair trading engine included in the system of FIG. 1 applies to fill a pair trade request FIG. 3 is a flowchart of the steps a pair crossing network included in the system of FIG. 1 applies to fill a pair trade request FIG. 4 is a flowchart of a process by which the pair crossing network of the system of FIG. 1 fills imperfectly matched orders and FIG. 5 is a graph for identifying the market prices for two securities that meet the required spread limits. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG. 1, there is shown a block diagram of a system 1 for trading securities in pairs according to the present invention. System 1 receives pair trade requests from clients operating client access devices 7 and attempts to fill the pair trade requests according to the parameters associated with the particular pair trade request. System 1 includes two different subsystems for filling pair trade requests: a pair trading engine 3 and a pair crossing network 5 . As will be described below, pair trading engine 3 receives a pair trade request and attempts to fill (in whole or in part) the trade request by executing the appropriate trades in an external market 13 (that may include, by way of non-limiting example, the New York Stock Exchange, the NASDAQ or any other financial market). Pair trading engine 3 may also fill (in whole or in part) a pair trade request by executing a transaction against order inventory 11 of (non-pair) trade requests controlled by the financial institution that is operating system 1 . In addition, pair trading engine may also fill (in whole or in part) a pair trade request by forwarding the trade request to pair crossing network 5 for matching with other pair trade requests. Likewise, pair crossing network 5 receives a pair trade request and fulfills (in whole or in part) the request by matching it against another pair trade request received by pair crossing network 5 . by matching the request against inventory 11 controlled by the financial institution andor by forwarding the trade request to pair trading engine 3 for execution in external markets 13 . System 1 also includes a portfolio manager 9 (that may be, for example, a software program executing on a computer system) that receives the pair trade requests from client access device 7 and presents the trade request to either pair trading engine 3 . pair crossing network 5 or both, depending on the trade parameters set by the client. Also, the client may query portfolio manager 9 regarding the status of any pair trade request the client has presented to system 1 . In operation, system 1 may fulfill a pair trade request either using pair trading engine 3 . or pair crossing network 5 . or a combination of the two. For example, a pair trade request received by system 1 may be completely filled by pair trading engine 3 as follows. Assume a case where XYZ is taking over ABC and is offering 0.575 shares of XYZ for each ABC share and investor Arb wants to invest in the price difference between ABC stock and XYZ stock. To take advantage of the price difference, Arb wants to lock in the difference between the value offered (0.575XYZ stock) and the value of ABC stock by buying ABC stock and selling XYZ stock subject to the condition that ABC0.575 XYZlt1.19 (i. e. Arb desires to capture a 1.19 difference between XYZs takeover offer and ABCs share price). In order to fill this pair trade, Arb presents a pair trade request to portfolio manager 9 (using client access device 7 ). The pair trade request typically includes a number of parameters that define the pair trade and that also may be used by portfolio manager 9 in determining how the pair trade request is to be filled. Arb typically indicates in the trade request the number of spreads the Arb desires to invest in and also provides a minimum and maximum share amount that he is willing to trade per tranche. For example, Arb may indicate a desire to invest in 100,000 spreads and may only wish to trade the spread 3,000-8,000 shares at a time. Arb generally sets this tranche size range based on the liquidity and volatility of ABC stock and XYZ stock. Arb may set a larger minimum tranche size if ABC stock and XYZ stock are fairly liquid stocks because higher liquidity increases the likelihood that a larger tranche size will be executed. Arb may set a lower maximum tranche size if XYZ stock and ABC stock are volatile stocks so as to limit the leg risk associated with executing a pair trade. Yet another pair trade parameter Arb provides is the spread limit (in the above case 1.19) which is the amount Arb desires to capture in the trade. Arb does not have to provide, however, the discrete prices at which trades for ABC and XYZ stock are to be executed as these prices are calculated by pair trading engine 3 (andor pair crossing network 5 ), as will be described below. Referring now to FIG. 2, there is shown a flowchart describing the steps pair trading engine 3 applies to fill a pair trade request. The flowchart in FIG. 2 is based on the above example and the market data listed in Table 1 below. Initially, in Step 201 . pair trading engine 3 determines whether the bidbid prices or askask prices of ABC and XYZ stock, respectively, meet the spread limit requirement of the particular pair trade request. In this case the bidbid spread is 1.4375((122.500.575)69) and the askask spread is 1.1969 ((122.6250.575)69.3125) so that each spread is less than the spread limit of 1.19, as is required for this particular trade. Once it is determined that either the bidbid spread or the askask spread meets the spread limit, then in Step 202 . it is determined (as is indicated in Table 1) how much XYZ stock can be sold at the bid and how much ABC stock can be bought at the ask. In an exemplary embodiment, the client may specify whether the bidbid spread, the askask spread or either the bidbid or the askask spread must exceed the indicated spread limit for a transaction to proceed. If neither the bidbid spread nor the askask spread meets the spread limit, the process waits a period of time (for example 0.10 seconds) and returns to Step 201 to again test whether the bidbid spread or the askask spread meets the spread limit. Next, in step 203 . an equivalent amount of stock that can be sent into the market (i. e. boughtsold in the market) is calculated for a spread based on the bidbid price spread andor the askask price spread that meets the spread limit. In this example, if a maximum of 10,000 shares of XYZ stock can be sold into the market (i. e. the XYZ bid size) then, based on the ABC:XYZ ratio (of 1:0.575 in this case), a total of 17,391 (10,0000.575) shares of ABC stock are to be bought in order to execute a balanced pair trade. Likewise, if a maximum of 1,500 shares of ABC stock can be bought in the market (i. e. the ABC ask size), then, based on the ABC:XYZ ratio (of 1:0.575 in this case), a total of 863 (15000.575) shares of XYZ stock are to be sold in order to execute a balanced pair trade. Next, in Step 204 . the pair trade share amounts calculated in Step 203 are adjusted to conform to the wave maximum and minimum parameters (i. e. the maximumminimum tranche size) included in the pair trade request as well as market round lot limits. In the above example, the amount of ABC shares to be bought that was calculated based on the XYZ bid size (i. e. 17,391) is first rounded to an even lot size (i. e. 17,400) and then reduced to the maximum tranche size of 8000. Also, the amount of XYZ shares to be offered that was calculated based on the ABC ask size (i. e. 863) is first rounded to an even lot size (i. e. 900) and then increased to 1,700 shares to meet the minimum tranche size of 3000 (30000.5751777). In an exemplary embodiment the minimum and maximum tranche size is scaled by the particular ratio (for example, in the above case, the tranche sizes for XYZ stock is scaled by 0.575). In another embodiment, the maximumminimum tranche size is used for each security in the pair trade request without scaling. In yet another exemplary embodiment, the pair trade request includes a separate maximumminimum tranche for each security. Once the share amounts for the pair trade are calculated, in Step 205 . the share prices that are needed to meet the spread limit of the pair trade request are calculated. For example, for a pair trade based on the bidbid price spread, in order to meet the spread limit of 1.19 credit, the price at which ABC stock is to be bid should be no greater than 69.2475 ((122.500.575)1.19) a share. Likewise, for a pair trade based on the askask price spread, in order to meet the spread limit, the price at which XYZ stock is to be offered should be greater than or equal to 122.6130 ((69.31251.19)0.575) a share. Next, once the pair trade share amounts and share prices have been calculated, in Step 206 . pair trading engine 3 sends initiating orders to external markets 13 in order to fill the pair trade request. The initiating orders may include an initiating order for executing a pair trade based on the bidbid spread (in this case a bid for 8,000 shares of ABC stock at 69.2475) andor an initiating order for executing a pair trade based on the askask spread (in this case an offer of 1,700 shares of XYZ stock at 122.6130). Finally, as the initiating orders sent to external markets 13 in Step 207 get filled, pair trading engine 3 automatically sends into the market the covering side of the pair trade. So, for example, as the initiating order of buying 8,000 shares of ABC stock at 69.2475 gets filled, pair trading engine 3 sends an order to external markets 13 to sell 4,600 (8,0000.575) shares of XYZ stock at 122.50. In an exemplary embodiment, the clients pair trade request includes threshold amounts that indicate the amount of variance in stock price andor share amount the client is willing to absorb. For example, if in the process of covering the initiating order the price of XYZ stock dips to 122.49 (in which case the spread limit of the pair trade would drop to 1.18), then pair trading engine 3 would still sell XYZ stock at the price of 122.49 if the 0.01 difference was within the threshold amount included in the pair trade request. Similarly, the pair trade request may include threshold amounts for any other pair trade parameter, including by way of non-limiting example, the number of spreads to be purchased and the tranche sizes. If, however, a particular threshold amount indicated by the client is exceeded for any given pair trade parameter, then pair trading engine 3 would attempt to cancel the initiating order andor the covering order (that may be possible if the orders have not yet reached the market or have not yet been filled). In such a case, pair trading engine 3 would then repeat the above analysis for determining suitable initiating and cover orders. To fill a pair trade request, pair trading engine 3 executes trades utilizing the method described above. Typically, pair trading engine 3 tranches a pair trade request and trades piece-meal in external markets 13 . In certain cases, however, it may be difficult to fill a trade request by executing several transactions in external markets 13 either because the pair trade request is for a very large number of spreads or includes stocks that are illiquid (in which cases pair trading engine 3 may be ineffective in filling the pair trade request). Also, in certain situations, a client wishing to remain anonymous may indicate in the pair trade request a preference that no orders be sent to external markets 13 . In these circumstances, portfolio manager 9 may route the particular pair trade request to pair crossing network 5 . Referring now to FIG. 3, there is shown a flowchart illustrating the steps pair crossing network 5 applies to fill a pair trade request. The flowchart in FIG. 3 is based on the above example and the market data listed in Table 2 below. Spread Limit as defined by 0.575 XYZ - ABC Continuing the previous example, assume the pair trade request issued by Arb for 100,000 spreads was half-filled by pair trading engine 3 . Also, assume that system 1 receives a pair trade request from Antiarb that indicates a desire to sell 30,000 shares of ABC and buy 17,200 shares (a ratio of 1:0.575) and also indicates a spread limit of 1.30 (i. e. (ABC0.575XYZ)lt1.30). In this case Arb and Antiarbs orders are complimentary in the primary order elementssecurities, ratios and buy versus sell. Also, Antiarb is willing to pay 0.11 per spread more than Arb is demanding from the marketplace. Based on these parameters, there is an opportunity for Arbs and Antiarbs trade requests to be filled via pair crossing network 5 . If Antiarbs pair trade request was marked for trading by pair trading engine 3 . then portfolio manager 9 sends Antiarbs order to pair trading engine 3 for execution. Pair trading engine 3 then sends the parameters of Antiarbs trade request, as well as all orders waiting for execution in pair trading engine 3 . to pair crossing network 5 . Pair crossing network 5 will recognize (as described above) that there is a crossing opportunity between Arbs order and Antiarbs order. In this case, pair crossing network 5 then directs pair trading engine 3 to suspend the execution of Antiarbs order in the amount that can be crossed by pair crossing network 5 (30,000 spreads in this case). In addition, pair trading engine 3 routes a cross amount of 30,000 spreads from Arbs order to pair crossing network 5 for crossing against Antiarbs order. At this point, the pair crossing network 5 crosses the Antiarb order against a portion of Arbs order, as follows. Assume the prevailing market conditions at the time of the cross are as shown in Table 3. Furthermore, Table 3 indicates the XYZ Ratio-Adjusted Value for both the bid and ask prices based on the conversion ratio of 1:0.575. Based on the XYZ Ratio-Adjusted Values, a Bid:Ask Spread Range (i. e. the spread provided for a cross between the bid price of ABC stock and the XYZ Ratio-Adjusted ask price) of 1.3863 is calculated and an Ask:Bid Spread Range (i. e. the spread provided for a cross between the ask price of ABC stock and the XYZ Ratio-Adjusted bid price) of 1.05 is calculated. To perform the cross, in Step 301 pair crossing network 5 first determines whether the range of spread limits associated with Arbs and Antiarbs trade requests (i. e. 1.30-1.19) coincides with the range of the prevailing market spread (1.3863-1.05). In this example, the range of spread limits does coincide with the prevailing market spread because at least a portion of the spread limit range overlaps with a portion of the market spread. Thus, a cross can occur. Next, in Step 302 . pair crossing network 5 calculates the mean of Arbs and Antiarbs spread order limit which is (1.301.19)21.245 and determines whether the mean is within the range of the market spread (i. e. 1.3863-1.05). If it is, then in Step 303 . pair crossing network 5 calculates the prices at which to cross. The prices must be within the current markets for ABC stock and XYZ stock, and satisfy market uptick requirements (for short sales), and provide a spread that is equal to the spread level calculated above. For example, with the inside market for ABC stock at 70.00-70.25 and the inside market for XYZ stock at 124.00-124.15, a cross price of 70.11 for ABC stock and 124.096 for XYZ stock provides the spread of 1.2452 thereby meeting the requirement of both Arbs and Antiarbs trade request. Finally, in Step 304 . pair crossing network 5 crosses 30,000 shares of ABC stock at 70.11 (with Arb buying and Antiarb selling) and 17,200 shares of XYZ at 124.096 (with Arb selling and Antiarb buying). If it is determined in Step 302 that the mean of Arbs and Antiarbs spread order limits does not fall within the range of the market spread, then in Step 305 . the spread closest to the mean of the two spread limits that is also within the market spread is calculated. For example, if the market spread is 1.3863-1.28, then the mean of the two spread limits (1.245) is not within the market spread. In such a case, 1.28 is selected as the spread level that is closest to the mean and within the market spread. In an exemplary embodiment, the spread level at which Arb and Antiarb cross can be determined in any other suitable manner as long as the spread level is within the market spread and within the range of spread limits indicated in the pair trade requests. Once the spread level is determined, the method proceeds to Step 303 in which pair crossing network 5 calculates prices to cross at that are within the current markets for ABC stock and XYZ stock and that meet the calculated spread level. In the case where the calculated spread level is 1.28, the cross will occur at a price of 70.08 for ABC stock and 124.1043 for XYZ stock. Finally, the method proceeds to Step 304 in which pair crossing network 5 performs the cross between Arb and Antiarb. Once a pair trade request is filled (or partially filled), the transaction details are reported to portfolio manager 9 and made available to the client operating client access device 7 . In the previous example, pair crossing network 5 crosses orders in which both Arb and Antiarb desire to trade the same pair of securities in the same ratio. In an exemplary embodiment, pair crossing network 5 executes a cross between two pair trade requests that are not perfectly matched. For example, assume that pair crossing network 5 receives the pair trade requests as shown in Table 4. Note that these two pair trade requests are imperfectly matched because each trade request uses a different ratio between ABC and XYZ stock. Arbs Spread Limit is defined by 0.575 XYZ - ABC. Antiarbs Spread Limit is defined by 0.6 XYZ - ABC. Also, assume the market in ABC and XYZ stocks at the time the pair trade requests are received by pair crossing network 5 is as described in Table 5 below. Arbs XYZ Ratio-Adjusted Value Arbs Dollar Range AntiArbs XYZ Ratio-Adjusted Value AntiArbs Dollar Range Referring now to FIG. 4, there is shown a flowchart illustrating a process by which pair crossing network 5 fills these imperfectly matched order. First, in Step 401 . pair crossing network 5 determines whether Arbs buy security equals Antiarbs sell security and whether Arbs sell security equals Antiarbs buy security. If both conditions are not met, then a cross between the two orders cannot occur. If the two conditions are met, then in Step 402 it is determined whether Arbs buy ratio equals Antiarbs sell ratio and whether Arbs sell ratio equals Antiarbs buy ratio. If these ratios are the same, then pair crossing network 5 proceeds to cross the two orders as described in the example above. Note that for a cross to occur at this stage does not require the ratios themselves to match but rather that the ratios of the ratios match (for e. g. a ratio of 2:3 matches a ratio of 0.667:1). If, however, the two ratios are not equal (as in this case where Arbs sell ratio does not equal Antiarbs buy ratio), then in Step 403 pair crossing network determines whether there is an overlap between Arbs and Antiarbs spread limit that also falls within the bidask market for ABC and XYZ stock. To make such a determination, pair crossing network 5 calculates whether there are market prices for both ABC and XYZ stock that satisfy the following inequalities: L 1lt(Ratio AABC )(Ratio BXYZ ) and (1) L 2gt(Ratio CABC )(Ratio DXYZ ) (2) Where L1 is Arbs spread limit of 1.19 credit, L2 is Antiarbs spread limit of 4.40 debit, RatioA is Arbs buy ratio of 1:1, RatioB is Arbs sell ratio of 1:0.575, RatioC is Antiarbs sell ratio of 1:1 and RatioD is Antiarbs buy ratio of 1:0.6. Referring now to FIG. 5, there is shown a graph 51 that depicts market prices for ABC and XYZ stock that meet the spread limits of Arb and Antiarb. In graph 51 . the x-axis represents the prices for XYZ stock while the y-axis represents the prices for ABC stock. Graph 51 includes a shaded area 53 that is the universe of market prices for ABC and XYZ stock that could satisfy the spread trade involving those stocks. Also included in graph 53 is a spreadlimit line L1 (inequality (1), above) that represents the spread limit associated with Arb and a spread limit line L2 (inequality (2), above) that represents the spread limit associated with Antiarb. Thus, the solution set of market prices that satisfies inequalities (1) and (2) is the portion of dark shared area 53 that falls between spread limit line L1 and spread limit line L2. In this example, a cross at a share price for ABC of 70.14 and a share price of 124.15 for XYZ stock meets the investors spread limits and falls within the market prices for ABC and XYZ stock. If it is determined that no share prices for both ABC and XYZ stock satisfy Arbs and Antiarbs spread limits, then no cross can occur. If such share prices do exist, then in Step 404 . it is determined which of the investors desires to transact in fewer shares of ABC stock and a mismatch in share amounts caused by the differing ratios is determined. In our example, Antiarb desires to sell fewer ABC shares than Arb desires to buy (30,000 vs. 50,000). Then, in Step 405 . pair crossing network 5 determines the number of XYZ shares that can be crossed between Arb and Antiarb based on the maximum amount of ABC shares that can be crossed (30,000 in this example). Based on the Antiarb ABC order quantity of 30,000 shares, the maximum number of XYZ shares that Arb will cross with Antiarb is: 30. 000 Arb XYZ Ratio Arb ABC Ratio 30. 000 0.575 1 17. 300 ( 17. 250 rounded to an even lotsize ). While the maximum quantity of XYZ shares that Arb will cross is 17,300, Antiarbs trade request indicates a desire to cross 18,000 shares. To overcome this imbalance, in Step 406 . pair crossing network 5 is in communications with external markets 13 for determining whether the excess 700 XYZ shares needed to satisfy Antiarbs trade request can be transacted for in external markets 13 . In an exemplary embodiment, pair crossing network 5 makes this determination by issuing a query to pair trading engine 3 as to whether 700 shares of XYZ stock can be bought in external markets 13 . Because, as indicated in Table 5, 3,000 shares of XYZ stock are offered at 124.15, pair trading engine 3 responds to pair crossing network 5 that the 700 shares needed to balance the cross between Arb and Antiarb are available from external markets 13 at 124.15. Next, in Step 407 . pair crossing network calculates the cross prices that are necessary such that Arb and Antiarb achieve their respective spread limits while also incorporating the excess 700 shares of XYZ stock that must be purchased from external markets 13 at 124.15 to satisfy Antiarbs trade request. An example of such cross prices that meet these criteria is a price of 70.14 for ABC stock and a price of 124.15 for XYZ stock. Once the cross prices are calculated, in Step 408 . pair crossing network 5 crosses 30,000 shares of ABC stock and 17,300 shares of XYZ stock between Arb and Antiarb and also buys 700 shares of XYZ stock at 124.15 in external markets 13 on behalf of Antiarb. Thus, both Arb and Antiarbs pair trade requests are satisfied. Alternatively, the entire 18,000 shares of XYZ stock may be crossed thereby fully satisfying Antiarbs trade request. In such a case, the ratio mismatch is addressed by Arb purchasing an additional 1200 (7000.575 rounded to a lotsize) shares of ABC stock from external market 13 or from firm inventory 11 . Once the trade is completed, the details of the transaction are provided to portfolio manager 9 to report the transaction details to the investors. In an exemplary embodiment, a pair order (or portion thereof) may be filled against an internal inventory 11 of trade requests maintained by the financial institution operating system 1 . For example, in the previous example in which an excess of 700 shares of XYZ stock needs to be purchased in order for a match (i. e. cross) between Arb and Antiarbs trade requests to occur, instead of determining whether the 700 shares are available in external markets 3 . pair crossing network 5 examines firm inventory 11 to determine whether the shares are available at the required price. Likewise, in cases where pair trading engine 3 desires to execute a pair trade based on orders to be sent to external markets 13 . pair trading engine 3 may first determine whether the order can be filled, in whole or in part, using trade requests pending in firm inventory 11 . Generally, the advantages of filling an order using pending trade requests in firm inventory 11 is that execution is faster, transaction costs are lower and leg risk is minimized. In another exemplary embodiment, a clients pair trade request may also include a minimum number of spreads that can be traded in pair crossing network 5 . Also, pair crossing network 5 may be designed to require a minimum share amount for a cross to occur. A minimum number of spreads that can be traded may be provided in order to reduce the distractions and booking costs associated with numerous smaller trades that may exceed the benefits of a de minimis fill. In another exemplary embodiment, portfolio manager 9 publishes the inside cross market for any pair that a client has selected for crossing in pair crossing network 5 . In still another exemplary embodiment, the client has the option for each pair trade selected for crossing in pair crossing network 5 to designate that the order should be reflected in the published inside cross market. This inside cross market consists of the tightest spread bid and offer (and corresponding bid size and offer size) from all client pair orders pending in pair crossing network 5 . In this way, a client can assess the likelihood and timing of a pair trade request being filled by pair crossing network 5 . Also, by publishing the clients spread interest, others seeking liquidity can trade at the clients level. In an exemplary embodiment, the client can designate each pair order designated for pair trading engine 3 andor pair crossing network 5 for Broker Negotiation. If Broker Negotiation is designated, the clients broker-dealer sales representative is notified of the clients spread order thereby prompting the broker-dealer to solicit a complementary, agency order from another client. The client may also designate each pair order for Broker Facilitation in which case the client allows the broker-dealer to act principally to fill the clients order. In summary, the advantages to a client of using pair trading engine 3 is that pair trading engine 3 allows the client to trade a spread order while limiting leg risk or the risk of missing a targeted spread level. This is accomplished by breaking the total order into tranches of sizes proportionate to the market, subject to user minimums and maximums, that can be traded in external markets 13 or against firm inventory 11 . Orders executed via pair trading engine 3 . however, are typically of a lower traded volume because trading is constrained to the liquidity available in the market. In contrast, trades executed via pair crossing network 5 are not constrained by market liquidity and do not have to be tranched to minimize leg risk. In particular, the benefits of filling a pair trade request via pair crossing network 5 are as follows: Elimination of Leg Risk. Pair crossing network 5 potentially provides a deeper well of liquidity because the trades are brokered, as a spread, directly between spread investors via a central clearing facility. Moreover, the introduction and use of a pair trading facility eliminates the leg risk described above without a sacrifice of liquidity. Large Transactions Only. Certain large investors may prefer to use pair crossing network 5 rather than pair trading engine 3 to avoid having a trade request broken up into numerous small executions. For example, sudden, brief moves in one of the two stocks included in the pair trade request may cause pair trading engine 3 to issue numerous small executions to fill the request. While a small investor may welcome capturing these small opportunities, a large investor may find such small executions to be more of a nuisance than a service. Price Setting versus Price Taking. Large investors seeking liquidity may prefer to set their price via the pair crossing network 5 . Also, other spread investors looking for liquidity can use pair crossing network 5 to monitor and trade with the large investor at the large investors level. While client orders directed to pair trading engine 3 can designate a spread limit, such orders are essentially price-takersas the market reaches the desired level, the orders are executed. Moreover, the pair trading engine tranching mechanism creates relatively small orders, allowing institutional flows to move the individual stocks. As a result, the small, tranched orders generated by pair trading engine 3 can become overpowered by single-name institutional flows. In addition, orders designated solely for pair trading engine 3 . and not for pair crossing network 5 . are not published to a central quote facility (such as by portfolio manager 9 ) thereby preventing other spread traders from knowing the size and limit of a pair trading engine order. Illiquid Stocks vs Liquid Stocks. Spreads that include one or two illiquid stocks are difficult to fill using pair trading engine 3 alone. Because illiquid stocks often demonstrate small bid and ask sizes and wide bid-ask spreads, pair trading engine 3 will typically only issue market orders having small quantities (subject to user minimums and maximums) that presents the client with greater leg risk from mid-trade changes in the bid-ask prices. In contrast, orders routed to price crossing network 5 are not confined by liquidity in the market place thereby allowing large crosses between spread traders in illiquid spreads. Accordingly, a system and method for trading pair securities is provided in which the client receives the benefits of having a pair order filled by either pair trading engine 3 . pair crossing network 5 or a combination of both. A number of embodiments of the present invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Based on the above description, it will be obvious to one of ordinary skill to implement the system and methods of the present invention in one or more computer programs that are executable on a programmable system including at least one programmable processor coupled to receive data and instructions from, and to transmit data and instructions to, a data storage system, at least one input device, and at least one output device. Each computer program may be implemented in a high-level procedural or object-oriented programming language, or in assembly or machine language if desired and in any case, the language may be a compiled or interpreted language. Suitable processors include, by way of example, both general and special purpose microprocessors. Furthermore, alternate embodiments of the invention that implement the system in hardware, firmware or a combination of both hardware and software, as well as distributing modules andor data in a different fashion will be apparent to those skilled in the art and are also within the scope of the invention. In addition, it will be obvious to one of ordinary skill to use a conventional database management system such as, by way of non-limiting example, Sybase, Oracle and DB2, as a platform for implementing the present invention. Also, network access devices can comprise a personal computer executing an operating system such as Microsoft Windows, Unix, or Apple Mac OS, as well as software applications, such as a JAVA program or a web browser. Access devices can also be a terminal device, a palm-type computer, mobile WEB access device or other device that can adhere to a point-to-point or network communication protocol such as the Internet protocol. Computers and network access devices can include a processor, RAM andor ROM memory, a display capability, an input device and hard disk or other relatively permanent storage. Accordingly, other embodiments are within the scope of the following claims. It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efficiently attained and, since certain changes may be made in carrying out the above process, in a described product, and in the construction set forth without departing from the spirit and scope of the invention, it is intended that all matter contained in the above description shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense. It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all statements of the scope of the invention, which, as a matter of language, might be said to fall therebetween. A Basic Introduction to Pairs Trading Pairs trading or Statistical Arbitrage is a stock trading strategy that attempts to be market neutral and capture the spread between two correlated stocks as they return to the mean price. It is known by some as 8220statistical arbitrage8221, but 8220pairs trading8221 is the more common name used to refer to this technique. Simply stated, it is the buying and simultaneous selling of two stocks that follow each other when they diverge from the normal pattern in the expectation that the normal pattern will soon resume. In other words, traders find two stocks that tend to move together. The trader would buy Stock A and sell Stock B short. Klicken Sie hier, um zu erlernen, wie man Bollinger Bänder mit einem quantifizierten, strukturierten Ansatz benutzt, um Ihre Handelsränder zu erhöhen und größere Gewinne mit dem Handel mit Bollinger Bands 8211 A Quantified Guide zu sichern. Pair trading is also done with options, futures, and baskets of stocks but that is fodder for future articles. This article will cover the basics of pairs trading by showing you a simple 4-step method for pairs trading. I8217ll also provide examples and point you in the right direction for more information on this highly effective stock trading tactic often used by trading professionals. Here is the simple 4 step method to get started in pair trading. Step 1. Choose the Stock Pair This may sound like the most difficult part of the process, but it8217s actually quite simple in its most raw form. There are numerous complicated methods for choosing the pair of stocks, but it all boils down to finding two stocks that are correlated in movement. Start out by looking for stocks that make sense to be similar. Here are several examples: These are just a tiny few of the stocks that can be used in pairs trading because of their correlation in movement. Step 2. Visually Confirm Correlation Using Charts Eyeballing price charts is a very basic way to determine correlation of pairs. Look at charts of stocks that you think should be correlated to find several that truly move together. There are many more complex ways to do this, but this way is the most simple. Step 3. Create a Price Ratio Chart This is another complicated sounding, but actually simple, procedure. Most charting platforms can do this for you automatically. A Price Ratio Chart It is a chart of both stocks plotted together. It is calculated by dividing one stock price into the other. These are normally line charts and measure deviation from the mean or average spread between the two stocks in the pair. Step 4. Buy One Stock. Sell One Stock Short When the price ratio line moves to its first or second deviation from the mean it8217s time to enter the trade. You want to go long the lagging stock and short the over performer. Your profit is anywhere in the spread as it comes back to the mean. When you start out, match dollar value in each stock and not share number, this keeps things equal in the moves. There are many ways to size the trades, this is just the most rudimentary method. This is pair trading in its most simple form. It8217s not a fool proof method. Händler können und verlieren Geld. However pairs trading is a proven method for consistent profits. Most importantly, remember to utilize stops when pair trading. It is possible that both sides of the trade can lose, so know how much you are willing to lose prior to executing your first pairs trade. Dave Goodboy is Vice President of Marketing for a New York City based multi-strategy fund.
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