The finished at 12,747 on July 21, fell to 10,719 on Aug. 10, rebounded to 11,529 on Wednesday before dropping to 10,953 on Thursday. The Nasdaq stock index has experienced a similarly erratic ride.
Some observers say automated computer systems can be blamed for at least part of the accelerated unpredictability of the markets
"[The recent] volatility is absolutely crazy," said IDC analyst David O'Dowd. "I don't know a better way to put it. We've seen record lows to record highs in a span of days, not months or years," O'Dowd said. "That's what electronic markets have done."
Up to 70% of trading volume is now consummated by computerized high-frequency trading systems, according to O'Dowd.
Dow Jones Industrial Index over the past three weeks