Black Monday is remembered as the 1987 crash day when the FTSE 100 suffered its largest one-day percentage fall.
On October 19, 1987, the FTSE 100 dropped 26.45%, while the Dow Jones Industrial Average fell 22.6% in the United States. The selling spread rapidly between financial centers through increasingly connected markets and communication systems.
The crash followed a period of strong share-price gains. Investors were worried about valuation, interest rates, currency tensions, and economic prospects. Automated trading and portfolio-insurance strategies also contributed to selling pressure, although historians and economists debate the weight of each factor.
Black Monday is a global label rather than a reference only to New York. The same date produced severe declines in Hong Kong, Australia, Britain, and the United States. “Black Tuesday” is associated with the 1929 Wall Street Crash, making the two names an important historical distinction.