Black Monday occurred on October 19, 1987, when U.S. stocks suffered their largest one-day percentage decline.
The Dow Jones Industrial Average fell 508 points, or 22.6%, in a single trading session. The decline was part of a worldwide market collapse that also affected Australia, Hong Kong, the United Kingdom, and other financial centers.
Several factors contributed, including high valuations, rising interest rates, trade tensions, and growing use of computerized trading strategies. Portfolio insurance programs could intensify selling when prices fell. Although the crash was severe, it did not produce a prolonged economic depression like the 1929 crash.
Black Monday is often confused with the 1929 market-break days called Black Thursday and Black Tuesday. The 1987 event was also distinct because markets recovered relatively quickly and the financial system remained functioning.