The Dow Jones Industrial Average suffered an intraday point drop of about 998.5 points during the 2010 Flash Crash.
On May 6, 2010, U.S. equity markets fell extremely rapidly before recovering much of the loss. The Dow's decline amounted to about 9 percent from its earlier level. Several major indexes and individual securities experienced extraordinary temporary price movements, including trades at implausibly low prices.
Investigations found that automated trading, stressed market conditions, and interactions among different trading systems played important roles. The U.S. Securities and Exchange Commission and the Commodity Futures Trading Commission later described a large sell order and subsequent algorithmic activity as central elements of the event. The crash exposed weaknesses in market structure and safeguards.
The 998.5-point figure describes the Dow's move from its intraday high to its low, not its final daily percentage loss. It is also different from the Dow's closing decline, which was much smaller because prices recovered before the session ended.