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SEC says best-price rule helped crowd stock exchanges
The agency argues Rule 611 gave every venue a path to the same protected-quote revenue. It points to 17 operating exchanges, plus three approved but not yet live, as evidence the market kept fragmenting.
For investors, the question is not just whether stocks trade at the right price. It is whether a rule built to keep markets orderly also helped turn U.S. equity trading into a crowded field of exchanges that all want a piece of the action.
In Washington, the Securities and Exchange Commission says Rule 611 of Regulation NMS, the National Market System framework, did more than police trades. By giving every exchange a shot at a protected quotation, the agency says, it also opened the door to market-data and connectivity revenue that made it easier for new venues to keep appearing.
A rule that paid for itself
The SEC’s argument is blunt: if an exchange could display a protected quote, it could also tap into the economic rewards attached to that status. That mattered even for small or low-volume venues, because the rule did not reserve those benefits for the biggest players.
The commission says that incentive structure helped lower barriers to entry across the market. In its telling, the rule did not just shape how trades moved. It helped shape how many places wanted to host them.
A crowded market with more doors
The agency points to the current exchange count as proof that the system has kept multiplying. There are 17 operating national securities exchanges that trade NMS stocks, along with three more that have approval but are not yet running.
That is the backdrop for the SEC’s proposal to revisit Rule 611. The issue is no longer only whether the rule protects the best price. It is whether it still makes sense in a market the agency says it helped fragment in the first place.