The S&P 500 lost about 34% during the global stock-market crash from February to March 2020.
The decline began after investors reacted to the spread of COVID-19, emergency public-health measures, business closures, and growing fears of a worldwide recession. The S&P 500 reached a record closing high on February 19, 2020, then fell to a low on March 23.
From its peak to that low, the index dropped approximately 34%, making the episode one of the fastest bear-market declines in modern market history. Trading was halted several times when U.S. exchanges hit circuit breakers designed to slow panic selling.
The crash was followed by a rapid rebound supported by fiscal stimulus, central-bank action, and expectations that vaccines and reopening would improve economic conditions. The S&P 500 is broader than the Dow and is commonly used as a gauge of large U.S. companies.