The SEC doubled the scope of stock trading curbs to include all companies in the Russell 1000 index, expanding a program meant to help prevent another plunge like the May 6 rout.
The announcement was made in a statement on the regulator's website. The volatility curbs had applied only to S&P 500 stocks. The Russell 1000 tracks shares of the biggest U.S. companies.
The program was implemented by U.S. exchanges after the May 6 stock market crash that erased $862 billion in less than 20 minutes. The curb halts a company's stock for five minutes after it rises or falls at least 10% within five minutes.
Seven stocks have been paused by the volatility circuit breaker: Intel Corp. on Aug. 27, Micron Technology Inc. on Aug. 5, Cisco Systems Inc. on July 29, Genzyme Corp. on July 23, Anadarko Petroleum Corp. on July 6, Citigroup Inc. on June 29 and Washington Post Co. on June 16.