U.S. stocks fell sharply as worries about a slowdown in the U.S. economy sparked a flight from risky assets to start the fourth quarter.

The Dow industrials fell 494 points, or 1.9%, following a 1.3% decline Tuesday. The S&P 500 dropped 1.8%, falling more than 1% in consecutive sessions for the first time this year. The last time it fell that much on back-to-back days was in December.

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