Which 1987 index recorded a one-day fall of 45.8% during the Black Monday crash?

The Hong Kong Hang Seng Index recorded a one-day fall of 45.8% during the Black Monday crash. Its collapse on October 19, 1987, was the largest percentage loss among the major markets associated with that global event.

Hong Kong’s plunge helped transmit fear westward as investors watched markets fall across time zones. The crisis then struck European exchanges and Wall Street, where the Dow Jones Industrial Average lost 22.6%. The Nikkei 225 and London’s FTSE 100 also suffered major declines, but neither matched Hong Kong’s percentage fall that day.

The 1987 crash involved high valuations, program trading, portfolio insurance, and concerns about interest rates and exchange rates. A common mistake is to use the Dow’s famous 22.6% statistic as the worldwide record. That number applies specifically to the Dow, while Hong Kong’s Hang Seng loss was substantially larger.