The 1987 global stock-market crash that began with a record 22.6% one-day fall in the Dow was Black Monday.
On October 19, 1987, the Dow Jones Industrial Average fell 508 points, or 22.6 percent, in its largest single-day percentage decline. Selling quickly spread to other major markets, including those in London, Hong Kong, and Australia.
Several factors contributed to the collapse. Valuations had risen strongly, interest rates were increasing, and investors used computerized portfolio-insurance strategies that could generate further selling as prices declined. International market links also allowed fear to move rapidly across time zones.
The crash did not develop into a depression like the crisis of 1929. Central banks supplied reassurance and liquidity, while market reforms later introduced circuit breakers and related controls. The 1987 episode is therefore both a major crash and an important turning point in the management of computerized market trading.