Black Monday, October 19, 1987, remains the largest one-day percentage loss in the Dow Jones Industrial Average.
The Dow fell 22.6% in a single trading session, a record percentage decline that has not been surpassed. Stock markets in other countries also suffered severe losses, making the event a genuinely international market crash rather than an isolated US episode.
Several factors contributed, including elevated valuations, investor anxiety, portfolio-insurance strategies, and computerized trading. As prices fell, automated selling could increase downward pressure. Later reviews did not identify one universally accepted single cause, but they emphasized the interaction of market structure, trading strategies, and fragile confidence.
Black Monday is often confused with the 1929 Black Tuesday crash. Black Tuesday was part of the Wall Street Crash of 1929, whereas Black Monday in 1987 set the Dow’s percentage-loss record. The two events also differed in their economic aftermath: the 1987 crash did not produce a depression comparable to the 1930s.