The S&P 500’s largest one-day percentage loss during the 2020 stock-market crash was about 12.0%, recorded on March 16, 2020.
Investors were reacting to the rapid global spread of COVID-19, escalating restrictions on economic activity, worsening forecasts, and extraordinary uncertainty. The S&P 500 fell 11.98% that day, its steepest single-session percentage decline since Black Monday in 1987.
The crash was unusually compressed. U.S. exchanges triggered market-wide circuit breakers four times in March 2020 as prices moved rapidly downward. The Federal Reserve and other authorities introduced major monetary and fiscal responses, and markets later rebounded sharply.
The 2020 crash is sometimes confused with the 2020 recession itself. The market collapse happened early in the pandemic shock, while the economic effects continued through changing public-health restrictions, supply disruptions, and employment losses.