GameStop frenzy leaves behind a mess for Wall Street regulators

Long before an army of small investors buying shares of GameStop shocked Wall Street, regulators saw the need for a clearer, real-time view of the trillions of dollars that sloshed through the markets each day.

In May 2010, a trader in London using an algorithm to manipulate a futures market helped trigger a chain reaction that wiped 9 percent off the Dow Jones industrial average in minutes. The market quickly recovered. But that “flash crash” underscored regulators’ urgent need for a tool that would allow them to pinpoint who was...