The S&P 500 fell 20.47 percent on October 19, 1987, the day known as Black Monday.
That decline was one of the sharpest single-day falls ever recorded by a major U.S. equity index. The S&P 500 tracks a broad selection of large U.S. companies, so its performance provides a wider market measure than the 30-stock Dow Jones Industrial Average.
The Dow’s better-known Black Monday statistic was a 22.6 percent decline, while the Nasdaq Composite fell about 11.5 percent. These percentages are often mixed up because all three indexes dropped during the same session, but each index has a different construction and stock weighting.
The crash was associated with high valuations, rising interest rates, currency and trade concerns, and computerized trading strategies. The Federal Reserve’s liquidity statement helped stabilize markets, and reforms later added trading pauses and other safeguards. The S&P 500 recovered its pre-crash closing level by 1989.