On October 19, 1987, the Dow Jones Industrial Average fell 22.6% in one trading session.
The decline occurred on the day commonly known as Black Monday. It was the largest one-day percentage fall in the Dow’s history, exceeding the percentage losses recorded during the most famous sessions of the 1929 crash. Selling spread across major international markets, making the event a global stock-market shock.
Several factors were investigated, including overvalued markets, rising interest rates, trade tensions, and computerized portfolio-insurance trading. No single explanation completely accounts for the episode. The market structure of the time also made it difficult for trading systems and participants to absorb the speed of selling.
The crash led regulators and exchanges to develop coordinated safeguards. In the United States, circuit breakers were introduced to pause trading after unusually large market moves. The Dow later recovered, and the 1987 crash did not produce an economic depression comparable to the 1930s.