The 1987 global stock-market crash was commonly called Black Monday after the Dow Jones Industrial Average fell 22.6% on October 19.
That one-session percentage decline remains the largest daily percentage fall in the Dow’s history. Selling began in Asia and spread through European markets before reaching the United States. The collapse was global: markets in Hong Kong, Australia, the United Kingdom, and other countries also suffered exceptionally large declines.
Several explanations have been studied, including high valuations, trade and currency tensions, rising interest rates, and computerized portfolio-insurance strategies that encouraged selling as prices dropped. The crash did not develop into a depression comparable to the 1930s. Central banks and market authorities responded, and the U.S. economy continued to expand for several more years. The event also encouraged reforms such as trading curbs, often called circuit breakers, designed to slow extreme falls and give investors time to reassess information.