During the 1987 global stock-market crash, the Dow Jones Industrial Average lost 22.6% on October 19.
The session became known as Black Monday and remains the largest one-day percentage decline in the Dow's history. The index fell 508 points, a dramatic loss relative to its level at the time. Selling spread rapidly from the United States to other major markets, making the event a global crash rather than an isolated Wall Street decline.
Several factors contributed, including high valuations, rising interest rates, trade tensions, and automated portfolio-insurance strategies. Computer-assisted selling could amplify falling prices, although no single cause fully explains the collapse.
The 22.6% figure is a percentage change, not the Dow's 508-point drop. That distinction matters because point losses depend on the index's level, while percentage losses allow comparisons across different eras.