The Securities and Exchange Commission approved a...

The Securities and Exchange Commission approved a six-month experiment limiting program trading on the New York Stock Exchange on days when the market takes a big swing either up or down. The SEC ordered that use of the exchange’s computerized SuperDOT system be suspended for the practice called “index arbitrage” when the Dow Jones industrial index rises or falls by 50 or morepoints. Traders use index arbitrage to make money by taking advantage of momentary price discrepancies between stock index futures and the underlying stocks.