Coola "Circuit Breakers Circuit breakers for stocks in the S&P 500 and Russell 1000 Index and almost 350 exchange-traded funds, introduced after the so-called flash crash, were extended today to all exchange- listed securities excluding options. While the current curbs halt trading when shares decline 10 percent within 5 minutes, 30 percent plunges trigger the circuit breakers for securities $1 or higher that weren?t previously covered by the restriction. Stocks less than $1 trigger the curbs when they drop 50 percent in 5 minutes. Last year?s disruption led to additional curbs to safeguard markets. Exchanges now require market makers to supply bids and offers within 8 percent of a stock?s prevailing price for the biggest companies during most of the trading day. Last year?s slump was exacerbated by shares of companies such as Accenture Plc plunging to pennies."