SEC changing rules for when exchanges halt trading

Bernard Madoff, chairman of Madoff Investment Securities, returns to his Manhattan apartment after making a court appearance Wednesday, Dec. 17, 2008 in New York. The judge in Madoff's fraud case has set new conditions for his bail, including a curfew and ankle-monitoring bracelet for the disgraced investor. (AP Photo/Jason DeCrow)
Jason DeCrow

(AP) WASHINGTON - Federal regulators are changing the rules for when a dramatic shift in value of the stock market or individual stocks triggers exchanges to halt trading.

The changes are aimed at curbing wild swings in prices such as occurred in the "flash crash" of May 6, 2010.

The Securities and Exchange Commission approved the changes, which were requested by the U.S. exchanges. The SEC said Friday they will take effect in a one-year pilot program to start by Feb. 4.

Flash crash: Full story finally revealed

One change affects circuit breakers, measures that automatically halt trading if the market falls by certain percentages. Circuit breakers will be triggered by smaller market declines than they are now, but the halts won't last as long.

In addition, rules for individual stocks will bar any trades outside specified price boundaries.