Amid the debate over how to prevent a recurrence of Aug. 24 2015, a trading day marked by delayed openings, more than 1,000 halts and wild price swings (more than $1 trillion in value was erased from the U.S. stock market that day). The ETF industry, as best as you can define it, has written an open letter to the SEC encouraging it to direct exchanges to harmonize the reopening of securities that have been in a so-called limit up/limit down halt, and clarify and align rules around clearly erroneous trades.