The U.S. market crash that began on October 19, 1987, when the Dow fell 22.6 percent in one day, was Black Monday.
On that Monday, the Dow Jones Industrial Average lost 508 points, equivalent to 22.6 percent of its value. It was the largest one-day percentage decline in the index’s history, and selling spread rapidly to other major markets around the world.
Analysts have identified several contributing factors, including high valuations, trade and interest-rate concerns, portfolio insurance, and computerized program trading. No single cause explains the scale of the decline, but automated selling may have accelerated the downward movement.
Black Monday is distinct from Black Monday in 1929, which refers to October 28 of that year. The 1987 crash did not produce a depression like the 1929 collapse, and monetary authorities responded quickly with liquidity support and reassuring statements.