On October 19, 1987, the Dow Jones Industrial Average fell approximately 22.6% in one trading session.
The day became known as Black Monday and remains the largest one-day percentage decline in the Dow’s history. The index lost 508 points, a dramatic fall given the market’s level at the time. Selling spread rapidly across international markets, including Hong Kong, London, and Australia.
Several forces contributed, including high valuations, rising interest rates, trade concerns, and automated portfolio-insurance strategies. Computerized selling could amplify a decline by generating additional sell orders as prices dropped. The exact causes remain debated, but the scale of the fall is not.
The 22.6% figure is a percentage decline, not a point loss. That distinction matters because index point losses depend on the index’s starting level. The crash also differed from 1929: the economy did not enter a Great Depression afterward, partly because central banks supplied liquidity and confidence recovered.