Market-wide circuit breakers are triggered when the broad-based S&P 500 falls by a certain amount within a single trading day, which halts trading across all markets. It can be triggered at three circuit breaker thresholds relative to the prior day’s closing price of the S&P 500, The first is Level 1 at 7%, followed by Level 2 at 13%, and 20% at Level 3. The purpose of circuit breakers is to stem excess market volatility.