Which stock exchange saw the largest single-day percentage loss during the 1987 global market crash?

The Hong Kong Stock Exchange saw the largest single-day percentage loss during the 1987 global market crash.

On October 19, 1987, Hong Kong's Hang Seng Index fell 46.2%, making the Hong Kong market's collapse especially severe. The panic then spread across international markets. The Dow Jones Industrial Average fell 22.6% in the United States, its largest one-day percentage decline, while other major exchanges also recorded extraordinary losses.

The episode became known as Black Monday, although the local calendar date differed in some markets because trading sessions occur across time zones. Automated trading, portfolio insurance, high valuations, and international market linkages were among the factors examined afterward.

The Hong Kong result is often overlooked because the American Dow decline dominates popular accounts. The Dow's 22.6% loss was the largest in its own history, but it was not the largest percentage fall recorded by a major exchange during that worldwide crash.