The first circuit breaker triggered in U.S. markets on March 9, 2020, was Level 1.
The S&P 500 fell 7% from its previous close shortly after trading began, activating a Level 1 market-wide circuit breaker. Trading paused for 15 minutes. The halt was designed to give investors time to absorb information rather than sell continuously during an exceptionally rapid decline.
The March 9 sell-off reflected growing concern about the COVID-19 pandemic and a sudden oil-price dispute between Saudi Arabia and Russia. It was the first U.S. market-wide trading halt triggered since the circuit-breaker system was revised after the 2010 Flash Crash.
Additional halts followed later in March as the crash continued. Level 2 is associated with a 13% S&P 500 decline, while Level 3 is associated with a 20% decline. These thresholds apply to market-wide declines during a trading session.