Which exchange closed for four days after Black Monday in 1987?

The Hong Kong Stock Exchange closed for four working days after Black Monday in 1987.

Hong Kong had suffered one of the sharpest market declines in the global crash. On October 19, the Hang Seng Index fell 420.81 points, while share values dropped about 45.8% over the broader October episode. Officials feared that continued losses could destabilize the exchange and overwhelm the futures market.

The Hong Kong Stock Exchange Committee and the Hong Kong Futures Exchange committee announced the closure the next morning. The pause ran for four working days, giving market participants time to address unsettled trades and mounting defaults. Trading resumed on October 26, but the Hang Seng Index then fell another 33.3% in one day.

The closure is sometimes loosely described as the exchange shutting for four days, although both the stock and futures markets were involved. It was an exceptional response: most other major markets remained open, using trading limits, liquidity measures, or other safeguards instead.