The U.S. Securities and Exchange Commission is convening a group of financial industry veterans for the first time next month to consider stock market reforms, but one group will be conspicuously absent: retail brokerages. The SEC’s 17-member Market Structure Advisory Committee includes representatives of fund companies, an exchange, off-exchange trading venues, dealers, and academia, among others. The group, which meets four times a year, will review old rules, and advise the SEC on a range of new regulations designed to make sure the market is as stable and fair as possible.