The worldwide stock-market plunge on October 19, 1987, was called Black Monday.
On that day, the Dow Jones Industrial Average fell 508 points, or 22.6%, the largest one-day percentage decline in its history. Markets in Hong Kong, Europe, Australia, and elsewhere also dropped sharply, making the event international rather than solely American. The decline followed a period of strong share-price growth, rising interest rates, trade tensions, and investor concern about valuations.
Computerized portfolio-insurance strategies and other program trading were widely examined after the crash because automated selling could intensify a falling market. However, no single cause fully explains the episode. The Federal Reserve, led by Alan Greenspan, responded by affirming its readiness to provide liquidity to the financial system. Despite the dramatic fall, the United States avoided a depression like that of the 1930s, and the economy continued expanding. Black Monday is sometimes confused with the October 1929 crash dates, but its defining date is October 19, 1987.