Hong Kong’s stock exchange suffered the world’s largest one-day percentage fall on October 19, 1987.
The Hang Seng Index dropped 46% during the Black Monday episode, making Hong Kong’s decline the most severe among the major markets affected that day. Trading was later suspended in Hong Kong for several days as authorities and market participants dealt with the turmoil.
The crash spread through increasingly connected international markets. Hong Kong fell first because of its time zone, followed by markets in Europe and North America. Australia also recorded a major fall, while the United States experienced the largest single-day percentage loss in Dow Jones history.
The Hong Kong result is sometimes overlooked because Black Monday is commonly associated with the United States. However, the event was global from the beginning. Its scale demonstrated how portfolio strategies, investor fear and cross-border capital flows could transmit a shock rapidly between exchanges.