Which 2010 event caused a brief trillion-dollar plunge in U.S. stock-market value?

The 2010 event that caused a brief trillion-dollar plunge in U.S. stock-market value was the 2010 Flash Crash.

On 6 May 2010, major U.S. equity indexes dropped rapidly and then recovered much of the loss within minutes. The Dow Jones Industrial Average fell about 1,000 points, or roughly 9%, during the session. Some individual securities briefly traded at extremely low or high prices before normal conditions returned.

U.S. regulators concluded that a large automated sell order interacted with high-frequency trading and market conditions to accelerate the decline. The event showed how electronic markets could transmit selling at extraordinary speed, even without a conventional economic collapse.

The Flash Crash differs from the 1987 crash and the 2008 crisis because it was exceptionally short-lived. It led to new safeguards, including tighter controls on clearly erroneous trades and more structured market-wide circuit breakers. Debate over the precise role of algorithms and liquidity providers continued after the official investigations.