"Two brokerage firms sold 200 to 300 contracts apiece beginning around 2:15 p.m. New York time, said Citigroup's Ruffat. The sales pushed prices lower in part because there were relatively few traders in the pit, he said. The decline caused futures to drop to prices at which other firms had pre-set sell orders, he said.
The retreat began at midafternoon in the pits of the Chicago Mercantile Exchange amid the sale of hundreds of Standard & Poor's 500 Index futures, said traders such as Citigroup Inc.'s Philip Ruffat. The September contracts declined far enough below the index's value to make it profitable to buy them and sell the underlying stock at the same time. "
