NEW YORK — The US Securities and Exchange Commission has unveiled a plan that protects markets from the kind of big price swings in stocks that triggered last year's "flash crash."


The new "limit up-limit down" safeguards, which the SEC unveiled Tuesday, would require trades in listed stocks to be executed within a range tied to recent prices for that security.

If approved by the SEC, the mechanism would replace the single stock circuit-breakers established through a pilot program shortly after the May 6 flash crash, which temporarily caused the stock market to lose over $1 trillion.

Share prices of stocks already covered by the current circuit-breaker program would only be allowed to move by up to five percent above or below their average values from the preceding five minutes.

Stocks in the S&P 500 index, Russell 1000 index and some exchange-traded funds are covered by the current pilot program. The SEC said all other stocks would be limited to a 10-percent trading band.

"Upgrading our trading parameters will help our markets retain the confidence of investors and companies," SEC chair Mary Schapiro said in a statement.

"We were focused on improving the structure of our markets before weaknesses were exposed on May 6, and we will continue to be focused on market structure going forward."

The SEC has been collaborating with national securities exchanges and the Financial Industry Regulatory Authority on the new proposal.