U.S. stock exchanges triggered Level 1 circuit breakers four times during March 2020.
The halts occurred on March 9, March 12, March 16, and March 18, 2020, as the COVID-19 pandemic produced extraordinary uncertainty about economic activity, corporate earnings, and energy markets. A Level 1 halt is triggered when the S&P 500 falls 7% from its previous close before 3:25 p.m. Eastern Time, pausing trading for 15 minutes.
The four March halts were the first uses of the U.S. marketwide circuit-breaker system since 1997. They were designed to give investors time to absorb information and reduce the risk of disorderly selling, not to prevent prices from eventually falling.
The episode is sometimes described as a single crash, but it was a sequence of violent sessions. The March 9 plunge also followed the collapse of an oil-production agreement and an oil-price shock. The S&P 500 ultimately reached its bear-market low on March 23, 2020, after the four circuit-breaker events.