The S&P 500 fell 33.9 percent from its February 2020 peak to the COVID-19 bear-market low.
The index reached a record closing level on February 19, 2020, before fears about the spreading coronavirus and its economic consequences drove a rapid global sell-off. The bear market low came on March 23, 2020, only 33 calendar days after the peak. This made the episode one of the fastest major market declines on record.
The fall reflected uncertainty about business closures, travel restrictions, supply-chain disruption, unemployment, and the likely duration of the pandemic. Central banks and governments responded with emergency monetary policy, fiscal support, lending programs, and public-health measures.
The 33.9 percent figure describes the S&P 500's peak-to-trough decline, not the loss on one day. The index then recovered rapidly from the March low, although the economic recession and uneven effects of the pandemic continued well beyond the market's initial rebound.