The 1987 stock-market crash’s largest one-day percentage decline is known as Black Monday.
Black Monday occurred on October 19, 1987, when stock markets around the world plunged. The Dow Jones Industrial Average fell 22.6 percent in a single session, its largest one-day percentage decline. The decline was not confined to the United States; markets in Europe, Asia, and elsewhere also suffered severe losses.
Several factors contributed, including overvalued markets, rising interest-rate concerns, international trade tensions, and computerized portfolio-insurance strategies. Those automated strategies could generate additional sell orders as prices fell, increasing pressure in an already nervous market.
Black Monday is sometimes confused with Black Tuesday of 1929. The names describe different crashes separated by 58 years. Unlike the 1929 crash, the 1987 collapse was followed by relatively rapid market recovery, helped partly by central-bank reassurance and changes to market safeguards.