The 19 October 1987 global stock-market crash was called Black Monday.
The Dow Jones Industrial Average fell 508 points, or 22.6%, in a single session. That remains the largest one-day percentage decline in the Dow's history. Markets in other countries also plunged, making the event an international crash rather than an isolated U.S. sell-off.
Several forces contributed, including rising interest rates, concerns about the U.S. trade deficit, overvalued shares, and computerized program trading. Portfolio insurance strategies were designed to limit losses but could generate more selling as prices dropped.
Black Monday is often confused with Black Tuesday, the major 1929 crash day. The 1987 episode did not produce a depression like the 1929 collapse, partly because central banks supplied liquidity and markets later recovered. Trading rules were subsequently changed, including the introduction of circuit breakers.