The SEC just broke a two-decade deadlock. On Monday, the commission gave Dimensional Fund Advisors (DFA) the go-ahead to create ETF share classes inside its mutual funds, a decision that investors, fund managers, and financial advisors have been chasing for years. The order, open for public feedback before finalization, lets DFA move forward and puts nearly 80 similar applications next in line. This is the same dual-class structure Vanguard had been running exclusively for over twenty years under a now-expired patent.