SIAC. A corporation owned two-thirds by the New York Stock Exchange and one-third by the American Stock Exchange. The corporation is under contract to receive trade information from the two exchanges and from their members for the purpose of assisting-- in final settlement. Data is also supplied to the Consolidated Tape Association (CTA), the Consolidated Quotation System (CQS), the National Security Clearing Corporation (NSCC), and the Intermarket Trading System (ITS). To perform this function, SIAC issues balance orders and continuous net settlement information to the members.