Which stock index plunged 45.8% during the October 1987 crash in Hong Kong?

The Hang Seng Index plunged 45.8% during the October 1987 crash in Hong Kong.

Hong Kong's market was among the hardest hit in the global Black Monday episode. Trading was suspended for several days after the collapse, and the Hang Seng Index recorded a fall of about 45.8 percent over the crisis period. The episode demonstrated how rapidly financial stress could cross borders through connected markets and investor expectations.

The Hong Kong crash was part of a worldwide sell-off rather than an isolated local event. Markets in the United States, Britain, Australia, and other economies also fell sharply. Concerns included high valuations, currency and interest-rate tensions, and computerized trading practices that could accelerate selling.

The Hang Seng Index tracks major companies listed in Hong Kong and is not the same as the Shanghai Composite or Shenzhen Component. Hong Kong's market history also includes later crashes, so the 45.8 percent figure belongs specifically to the 1987 global event.