The 1987 Black Monday crash caused the Dow Jones Industrial Average’s largest one-day percentage fall on October 19, 1987.
The Dow dropped 508 points, or 22.6%, in a single trading session. That percentage loss remains a landmark statistic in U.S. stock-market history, even though later crashes produced larger point declines because the index had become much bigger.
Several forces contributed to the panic, including concern about economic conditions, rising interest rates, and computerized portfolio-insurance trading. Selling accelerated rapidly as investors and trading systems responded to falling prices. The crash was not the same event as the 1929 Wall Street Crash, although both became associated with memorable “Black” days.
Afterward, U.S. exchanges introduced coordinated trading halts known as circuit breakers. These measures were designed to give investors time to assess information during unusually sharp falls, rather than allowing an unchecked feedback loop of automated and human selling.