The S&P 500 fell about 34% during the COVID-19 stock-market crash from its February 19, 2020 peak to its March 23 low. The decline was one of the fastest bear-market collapses in modern U.S. financial history.
Investors reacted to the spread of COVID-19, business closures, travel restrictions, and uncertainty about the economic consequences of the pandemic. An oil-price dispute between Saudi Arabia and Russia added pressure to markets in early March, although the pandemic was the dominant shock.
Trading was halted several times in March when U.S. indexes fell far enough to activate circuit breakers. Central banks and governments then announced extraordinary monetary, fiscal, and public-health measures. The S&P 500 recovered rapidly compared with many earlier crashes, though the economic effects were severe.
The S&P 500 tracks 500 large companies listed in the United States. It is often treated as a broad measure of U.S. large-cap equities, unlike the narrower, price-weighted Dow Jones Industrial Average.