March 9, 2020, was the first day the U.S. stock market’s modern circuit breakers were triggered during the pandemic sell-off.
The S&P 500 fell 7% shortly after trading began, activating a Level 1 market-wide circuit breaker and halting trading for 15 minutes. The plunge followed growing concern about COVID-19 and a collapse in oil prices after a breakdown in cooperation between major oil-producing countries.
Circuit breakers are designed to interrupt exceptionally rapid declines and give investors time to reassess orders. The U.S. system had been created after the 1987 crash and later revised, including changes to the thresholds and procedures.
The market also triggered the circuit breaker on March 12 and March 16, 2020. March 23 was the S&P 500’s closing low, but it was not the first circuit-breaker date of the episode.