The 2020 S&P 500 bear market took 16 trading days to reach a 20% decline from its peak.
The S&P 500 closed at a record high on February 19, 2020. As investors reacted to the expanding COVID-19 pandemic, travel restrictions, shutdowns, and fears of a global recession, the index fell rapidly. On March 12 it entered a bear market, conventionally defined as a decline of at least 20% from a recent closing high.
That 16-trading-day descent was the fastest bear-market entry in the index's history up to that point. The crash included several trading halts, known as circuit breakers, as prices moved violently. The Federal Reserve and governments introduced large monetary and fiscal responses.
The market then rebounded sharply, although the economic damage and public-health crisis continued. A bear market describes the index's price decline; it does not mean every stock fell by exactly 20% or that the economy had already reached its worst conditions.