Circuit Breakers and Volatility Halts

Market-wide circuit breakers trip at 7, 13 and 20 percent declines in the S&P 500, while single-stock bands halt individual names far more often.

Circuit breakers are pre-set rules that pause trading, either across the entire market or in a single stock, once price movement crosses a defined threshold. They exist to give participants a forced window to reassess rather than let a fast decline feed on itself through automated selling with no pause for new information to reach the market.

U.S. market-wide circuit breakers are tied to the S&P 500 index and were rebuilt after the May 6, 2010 flash crash, when the Dow Jones Industrial Average fell by roughly 9 percent within minutes before largely recovering the same afternoon. The current framework uses three decline levels measured against the prior session's closing value, each triggering a different response, and every exchange trading a listed U.S. security is required to observe the same halt at the same moment.

The levels are recalculated every morning against the prior close, so the same 7 percent threshold corresponds to a different absolute point move in the index depending on where the market closed the day before. This design keeps the trigger meaningful across very different market levels rather than pinning it to a fixed number of index points that would become stale as the index rises or falls over time.

A Level 1 decline of 7 percent triggers a 15-minute market-wide trading halt if it occurs before 3:25 p.m. Eastern time. A Level 2 decline of 13 percent triggers another 15-minute halt under the same time condition. A Level 3 decline of 20 percent halts trading for the remainder of the session entirely, regardless of what time it occurs. These thresholds apply to the S&P 500's decline from the prior day's close and are recalculated each morning against that reference point.

The 3:25 p.m. cutoff exists because a 15-minute halt triggered too close to the 4:00 p.m. close would leave too little time for the market to reopen and trade in an orderly way before the session ends, so a Level 1 or Level 2 breach after that time does not pause trading at all and the market is left to close on its own.