A circuit breaker is a mechanism in which the U.S. stock market is trading, and the market price falls sharply until it hits the circuit breaker, causing the stock market to suspend trading.。

On May 11, U.S. bank stocks fell, and PacWest Bancorp fell more than 34% at the beginning of the session, triggering a meltdown mechanism.。Since this month, the stock price has dropped 53.69%, was cut in half, the whole year has fallen nearly 80%。