Rule 606 of Regulation NMS requires: A each market center to prepare monthly electronic reports about its quality of executions and effective spreads B each broker-dealer to prepare quarterly reports on its routing of non-directed orders, including the 10 largest venues where orders were routed C market makers in OTC stocks to display any customer limit orders that are better-priced than the dealer’s own quote D any order execution facility to execute the order at the NBBO, even if that execution facility is posting an inferior quote