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The S&P 500 opened below its 200-day moving average, a key technical level.
The Dow fell 506.21 points, or 2.11 percent, to 23,527.15. The S&P lost 40.75 points, or 1.56 percent, to 2,573.7. The Nasdaq Composite dropped 126.95 points, or 1.83 percent, to 6,814.33.