Which event caused the fastest bear market in U.S. stock-market history during early 2020?

The COVID-19 pandemic caused the fastest bear market in U.S. stock-market history during early 2020.

As the coronavirus spread internationally, governments introduced travel restrictions, business closures, and social-distancing measures. Investors rapidly repriced expectations for corporate earnings, employment, trade, and economic activity. The S&P 500 entered a bear market on March 12, 2020, and reached its 2020 closing low on March 23.

The decline was unusually compressed: U.S. equity indexes fell from record highs to bear-market territory in weeks. Trading halts, known as circuit breakers, were triggered several times in March as prices dropped sharply. Central banks and governments then announced extensive monetary and fiscal support, while progress toward vaccines helped markets recover later in the year.

The crash is often called the 2020 stock-market crash or the coronavirus crash. It was distinct from the 2008 crisis, which originated in financial and housing markets, even though both episodes produced severe market volatility.