The New York Stock Exchange suffered its largest one-day percentage fall on October 19, 1987, known as Black Monday.
On that day, the Dow Jones Industrial Average fell 22.6 percent, while major markets in Europe, Asia, and elsewhere also recorded severe losses. The decline was not confined to one country, making the event an early example of a modern globally connected market crash.
Several forces were involved, including investor anxiety about valuations, interest rates, trade tensions, and the dollar. Computerized portfolio-insurance strategies and other automatic selling mechanisms amplified the downward movement. The exact relative contribution of each factor remains debated.
The crash did not lead to a depression comparable to the 1930s. Central banks supplied reassurance and liquidity, and the U.S. economy continued to expand. Regulators later introduced circuit breakers and other safeguards intended to slow trading during extreme price movements.