The S&P 500 lost 20.5% on October 19, 1987, during the Black Monday crash.
Black Monday produced extraordinary losses across U.S. markets. The Dow Jones Industrial Average fell 22.6%, while the broader S&P 500 dropped 20.5%. The decline was global: stock exchanges in Asia, Europe, and other regions also recorded major falls as investors reacted to interconnected economic and financial pressures.
The S&P 500 tracks large U.S. companies across many industries, so its loss is often used to show the breadth of the crash. The Dow’s larger percentage decline is more commonly quoted because it set a record for that index. The two figures describe different indexes and should not be substituted for each other.
After the crash, regulators examined trading systems, derivatives, and computerized portfolio strategies. The response included coordinated market reforms and the eventual adoption of circuit breakers to interrupt extreme selling.