Which stock-market index suffered the famous 22.6% one-day fall on Black Monday in 1987?

The Dow Jones Industrial Average suffered the famous 22.6% one-day fall on Black Monday in 1987.

On October 19, 1987, the Dow dropped 508.32 points, equivalent to 22.61% of its previous closing value. The decline was the largest one-day percentage fall in the index’s history and remains a defining statistic of the crash.

Stock markets around the world also plunged. Explanations examined afterward included overvalued shares, rising interest rates, trade tensions, a widening U.S. trade deficit, and computerized portfolio-insurance strategies that automatically sold futures as prices fell.

The event helped drive major changes in market infrastructure. U.S. exchanges later introduced circuit breakers, which temporarily halt trading during unusually rapid declines. The Dow recovered relatively quickly compared with the years-long recovery after 1929, showing that a dramatic single-day collapse does not always produce a decade-long depression.