The S&P 500 fell 33.9% from its February 19, 2020 peak to its March 23 trough during the COVID-19 crash.
The index closed at 3,386.15 on February 19 and reached 2,237.40 on March 23. That 1,148.75-point decline produced the commonly cited 33.9% peak-to-trough loss. The fall pushed the S&P 500 into a bear market with extraordinary speed.
The sell-off reflected escalating pandemic fears, business shutdowns, collapsing economic expectations and an oil-price shock. Trading was so volatile that U.S. market-wide circuit breakers were triggered several times in March, temporarily pausing activity after sharp declines.
A common mix-up is confusing the S&P 500's 33.9% drop with the Dow Jones Industrial Average's larger decline of about 37% over its corresponding period. The S&P 500 then rebounded rapidly and recovered its pre-crash closing high in August 2020, although the economic damage continued well beyond the market's low.