The Dow Jones Industrial Average lost 22.6% on Black Monday, October 19, 1987, during the global stock-market crash.
The fall was the largest one-day percentage decline in the Dow’s history. The selling began in Hong Kong, spread through European markets, and reached the United States after the New York Stock Exchange opened. The Dow dropped 508 points, from 2,246.74 to 1,738.74.
Several factors contributed, including concerns about overvalued shares, rising interest rates, a weakening U.S. dollar, and growing use of computerized trading strategies. Portfolio insurance programs accelerated selling as prices fell.
The 22.6% figure is often confused with the 1929 Wall Street Crash, but the 1987 decline was much larger as a single-day percentage loss. Despite the dramatic drop, the market later recovered, and the crash did not produce a depression comparable to the 1930s.