Which stock exchange saw the largest one-day percentage fall during the global Black Monday crash of 1987?

The Hong Kong Stock Exchange saw the largest one-day percentage fall during the global Black Monday crash of 1987.

On October 19, 1987, Hong Kong’s market fell sharply, and the shock moved westward through international financial centers. The Hong Kong Stock Exchange lost more than 45 percent over the crash period, making it one of the most severely affected major markets. The exact comparison depends on whether a source measures a single session or the broader sequence of declines, so the wording of the statistic matters.

The New York Stock Exchange is more famous because the Dow Jones Industrial Average fell 22.6 percent that day. However, Black Monday was international from the outset. Markets in Australia, the United Kingdom, Canada, and Japan also experienced major losses, demonstrating how closely linked global exchanges had become.