During Black Monday in 1987, the Dow Jones Industrial Average fell approximately 22.6 percent.
The decline occurred on 19 October 1987, when the Dow lost 508 points in a single trading session. Because the index stood at roughly 2,246 points at the previous close, the point loss represented an unprecedented percentage drop for the U.S. blue-chip index.
The fall was not limited to the United States. Equity markets around the world also plunged, making Black Monday a global crash rather than an isolated Wall Street event. Analysts have linked the panic to high valuations, macroeconomic concerns, portfolio insurance, and computerized selling, although historians do not identify one universally accepted cause.
The 22.6 percent figure refers to the Dow's percentage decline, not the percentage loss of every market or the full decline over the entire 1987 bear market. It remains larger than the one-day percentage losses recorded during the 1929 crash.