The Dow Jones Industrial Average fell 22.6% on October 19, 1987, the stock-market day known as Black Monday.
The decline was the largest one-day percentage fall in the Dow’s history. The index dropped 508 points, which was a record point loss at the time, but the percentage figure is the more useful comparison because index levels change over decades. Selling spread rapidly across international markets, making the event a global crash rather than a problem confined to New York.
Several factors contributed. Markets had risen strongly, valuations were high, and investors worried about interest rates, trade tensions, and economic conditions. Computer-assisted trading and portfolio-insurance strategies could also generate additional sell orders as prices declined. Economists still debate the exact weight of each factor.
Unlike the 1929 crash, Black Monday did not lead to a Great Depression. The Federal Reserve supplied liquidity, and the market eventually recovered. Regulators later introduced or strengthened circuit breakers designed to pause trading during extreme declines.