The Dow Jones Industrial Average fell approximately 22.6% on Black Monday in 1987.
On 19 October 1987, the Dow dropped 508 points, its largest one-day percentage decline at the time. The fall represented 22.61% of the index’s previous closing level and spread rapidly through financial markets around the world. Hong Kong, London, and other exchanges also suffered severe losses during the episode.
Several explanations have been studied, including international market contagion, investor anxiety, program trading, portfolio insurance, and overvaluation after a long rise. No single explanation fully accounts for the speed and scale of the decline.
The 1987 crash differed from 1929 in an important way: it was followed by a relatively short recession rather than a decade-long depression. The Federal Reserve supplied liquidity and reassured markets, while later reforms introduced coordinated trading halts and circuit breakers.