The Dow Jones industrial average dropped 198.67 points, or 1.6%, to close at 11,997.70, last night.
The drop was the worst since November 23 and ended a three-day run of modest gains. The last time the Dow closed below 12,000 was November 29.
The Standard & Poor’s 500 index fell 26.66, or 2.1%, to 1,234.35. The Nasdaq lost 52.83, or 2%, to 2,596.38.