The 1987 global stock-market plunge, including the Dow Jones Industrial Average’s 22.6% one-day fall, was Black Monday.
Black Monday occurred on 19 October 1987. The Dow’s percentage decline remains the largest single-day percentage loss in its history. Markets in Hong Kong, Australia, the United Kingdom, Canada, and other countries also suffered severe falls, making the episode international rather than solely American.
Several factors were discussed afterward, including high valuations, trade and currency tensions, investor fear, and computerized portfolio-insurance strategies. Those automated strategies could reinforce selling when prices dropped. Regulators later introduced circuit breakers and other mechanisms intended to slow disorderly declines.
Black Monday is often confused with Black Tuesday, the key date of the 1929 Wall Street Crash. It is also different from the 2010 Flash Crash, which was a brief intraday market disruption rather than a worldwide one-day collapse on the same scale.