On November 15, 2000, the SEC adopted new rules aimed at improving public disclosure of order execution and routing practices. As a result of Rule 11Ac1-5, market centers that trade national market system securities must make monthly, electronic disclosures of basic information concerning their quality of executions on a stock-by-stock basis, including how market orders of various sizes are executed relative to the public quotes and information about effective spreads - the spreads actually paid by investors whose orders are routed to a particular market center. In addition, market centers must disclose the extent to which they provide executions at prices better than the public quotes to investors using limit orders.
Data is available on WRDS through 2005, and is no longer updated.
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