The global stock-market plunge that began in Hong Kong in 1987 is known as Black Monday.
Hong Kong’s market fell sharply on October 19, 1987, and the selling spread westward through international financial centers. By the time New York trading ended, the Dow Jones Industrial Average had lost 22.6%, its largest one-day percentage decline. Australia, the United Kingdom, and other markets also experienced severe falls.
The name “Black Monday” is therefore used for the worldwide crash, not only for one American exchange. The exact calendar date was October 19 in the United States, while time-zone differences meant that the shock appeared on different local dates elsewhere.
Researchers have identified several contributing factors, including high valuations, macroeconomic concerns, currency tensions, and computerized trading strategies. The event did not produce a repeat of the Great Depression, and central-bank reassurance helped prevent a prolonged collapse in the banking system.