Which U.S. stock exchange experienced a record one-day percentage loss on October 19, 1987?

The New York Stock Exchange experienced a record one-day percentage loss on October 19, 1987. That date became known as Black Monday, when the Dow Jones Industrial Average fell 22.6%, its largest one-day percentage decline.

The decline occurred in an international wave of selling. Hong Kong’s market fell first, and losses spread through Europe before reaching the United States. Program trading, portfolio insurance, valuation concerns, rising interest rates, and international trade tensions were among the factors examined after the crash.

The New York Stock Exchange itself did not lose 22.6% as an index; that figure refers to the Dow Jones Industrial Average, a price-weighted index of selected companies. The exchange was the principal U.S. trading venue involved in the event. Regulators later introduced or strengthened mechanisms such as circuit breakers to pause trading during extreme declines.