The 1987 Black Monday crash occurred on October 19, 1987, when the Dow Jones Industrial Average fell 22.6% in one trading session.
The decline was the largest one-day percentage fall in the Dow's history. Selling spread rapidly through international markets, and stock exchanges in the United Kingdom, Hong Kong, Australia, and elsewhere also suffered severe losses. The scale of the fall made the date one of the most recognizable events in modern financial history.
Several forces contributed, including high valuations, rising interest rates, trade tensions, and computerized trading strategies. Portfolio insurance programs could increase selling as prices dropped, although researchers continue to debate the relative importance of each factor. The crash did not lead to a depression like the 1929 collapse, partly because central banks and market regulators responded quickly. The New York Stock Exchange later introduced circuit breakers to pause trading during extreme declines.