Which stock index lost about 22.6% on October 19, 1987, in the largest one-day percentage fall in its history?

The Dow Jones Industrial Average lost about 22.6% on October 19, 1987, during the Black Monday crash.

The decline was the Dow’s largest one-day percentage loss in its history. It occurred amid international market falls, concerns about overvaluation, trade tensions, rising interest rates, and widespread use of computerized trading and portfolio-insurance strategies.

The fall was global rather than confined to New York. Markets in Hong Kong, Australia, the United Kingdom, and many other countries also suffered severe losses. The U.S. economy did not enter a depression comparable to the 1930s, and the Dow eventually recovered.

The percentage figure is more important than the point loss when comparing crashes across eras. A modern index can lose many more points while representing a smaller percentage decline than Black Monday’s 22.6%.