Which stock-market index lost about 22.6% on Black Monday in 1987?

The Dow Jones Industrial Average lost about 22.6% on Black Monday in 1987.

The fall occurred on October 19, 1987, when the Dow dropped 508 points, its largest one-day percentage decline in history. Stock markets in Europe, Asia, and elsewhere also plunged, making the event a global crash rather than an isolated New York episode.

Several explanations were discussed, including computerized program trading, portfolio insurance, overvalued shares, rising interest rates, and international market tensions. No single cause has been universally accepted as a complete explanation.

The crash differed from 1929 in an important way: the United States economy did not enter a decade-long depression afterward. The Federal Reserve supplied liquidity, financial safeguards were reviewed, and the Dow eventually recovered. The S&P 500 and other indexes also fell sharply, but the famous 22.6% figure specifically refers to the Dow.