During the 1987 Wall Street Crash, the Dow Jones Industrial Average fell 22.6% on October 19. This was the largest one-day percentage decline in the index’s history, and the date became known as Black Monday.
The fall followed a sharp market rise earlier in the year, growing concern about interest rates, and worries about the value of U.S. stocks. Selling spread rapidly through international markets, including Hong Kong, London, and Australia, as financial markets became increasingly interconnected.
The decline was measured from the Dow’s closing level on October 16 to its close on October 19. The crash did not lead to a repeat of the Great Depression, although it caused major concern about the stability of financial markets.
The 22.6% figure refers specifically to the Dow’s one-day percentage loss, not the total decline during the entire 1987 bear market. The Dow later recovered, while regulators introduced measures such as circuit breakers to help slow future disorderly selling.