The Dow Jones Industrial Average fell approximately 22.6% during the 1987 Black Monday crash.
On October 19, 1987, the Dow dropped 508 points, or 22.6 percent, in a single trading session. It was the largest one-day percentage decline in the index's history, exceeding the percentage falls seen during the early stages of the 1929 crash.
The sell-off spread rapidly across international markets. Concerns about overvalued shares, rising interest rates, trade tensions, and automated portfolio strategies contributed to the panic. Program trading and portfolio insurance were widely debated because they could amplify selling in a falling market.
The crash did not produce a depression comparable to the 1930s. The Federal Reserve supplied liquidity, and markets eventually recovered. The episode nevertheless led exchanges and regulators to develop circuit breakers, which temporarily halt trading after unusually large price movements.