The sharp worldwide market decline that began on October 19, 1987, is known as Black Monday.
The name refers specifically to the date on which stock prices collapsed across major financial centers. The Dow Jones Industrial Average lost more than one-fifth of its value in a single day, while markets in London, Hong Kong, Australia, and elsewhere also recorded severe falls. Because the markets operated across time zones, the sell-off unfolded as a global chain.
Several explanations have been proposed, including overvalued shares, fears about interest rates and trade imbalances, and computerized trading strategies. Portfolio insurance programs automatically sold futures as prices fell, potentially increasing downward pressure.
The crash differs from the 1929 Wall Street Crash in both cause and aftermath. Central banks supplied reassurance and liquidity, and the 1987 decline did not produce a decade-long depression. The event led exchanges and regulators to introduce circuit breakers that can temporarily halt trading.