Which U.S. exchange-traded fund suffered the biggest one-day loss during the 2010 Flash Crash?

The iShares Russell 1000 Value ETF suffered the biggest one-day loss among the securities highlighted in investigations of the 2010 Flash Crash.

On May 6, 2010, U.S. markets plunged rapidly before recovering much of the decline. The Dow Jones Industrial Average briefly fell about 1,000 points, an unusually large move for a single trading session at that time.

The event affected stocks, exchange-traded funds, futures, and options. Some securities experienced trades at extremely low or high prices, while exchanges later canceled many clearly erroneous transactions. Investigations emphasized the interaction of automated trading, liquidity withdrawal, and a large sell order.

The Flash Crash differed from a conventional bear market because much of the movement happened within minutes and prices recovered quickly. Regulators subsequently introduced measures including circuit breakers and rules intended to address extraordinary volatility.