During the 1987 Black Monday crash, the Dow Jones Industrial Average fell 22.6% in one trading day.
The decline occurred on Monday, October 19, 1987, after substantial losses had already appeared in other markets. In point terms, the Dow dropped 508 points, a striking move for an index whose level was far lower than today’s. The percentage loss remains the largest single-day fall in the Dow’s history.
The crash was international: stock markets in Hong Kong, Australia, the United Kingdom, and elsewhere also plunged. Analysts have debated the precise combination of causes, including computerized trading strategies, portfolio insurance, investor overconfidence, and concerns about currency and interest rates. The phrase “one-day crash” therefore describes the most dramatic session, not the entire global decline.
Afterward, U.S. regulators introduced or strengthened safeguards including trading curbs, often called circuit breakers. These mechanisms were designed to pause trading during unusually rapid falls and give investors time to assess information instead of amplifying panic.