The securities and futures exchanges have procedures for coordinated cross-market trading halts if a severe market price decline reaches levels that may exhaust market liquidity. These procedures, known as market-wide circuit breakers, may halt trading temporarily or, under extreme circumstances, close the markets before the normal close of the trading session.
“A cross-market trading halt can be triggered at three circuit breaker thresholds — 7% (Level 1), 13% (Level 2), and 20% (Level 3). These triggers are set by the markets at point levels that are calculated daily based on the prior day’s closing price of the S&P 500 Index