Hong Kong’s stock exchange suffered the largest one-day percentage fall during the 1987 Black Monday shock.
On October 19, 1987, Hong Kong’s Hang Seng Index fell 45.8%. The collapse came as the selling that began in the United States spread across international markets and trading hours.
The shock then moved through markets in Europe, North America, and the Pacific. Australia, Spain, the United Kingdom, and the United States all recorded severe losses, but Hong Kong’s percentage decline was the most dramatic among major exchanges cited in accounts of the crash.
The event showed how closely linked global financial markets had become. It also encouraged exchanges and regulators to introduce safeguards such as circuit breakers, which temporarily halt trading during exceptionally sharp movements.