There were weak corporate results, the looming end of stimulus from the Federal Reserve and tensions between the West and Russia. The plunge snapped a string of five straight monthly gains, and pushed the blue-chip index to a slight loss for the year. The stock market fell in early trading after a dose of bad earnings news, and the losses accelerated throughout the day. Yum Brands, the owner of KFC and Pizza Hut, slumped after it said that its earnings would be crimped by a food safety scandal in China that involved repacked meat. Exxon Mobil stock fell $4.31, or 4.2 percent, to $98.94 after the energy company said that oil and gas production slipped 6 percent in the second quarter, disappointing analysts. Paul Zemsky, chief investment officer of Multi-Asset Strategies and Solutions at Voya Investment Management, said the main driver behind Thursday's sell-off was a reassessment of the outlook for interest rates in the U.S. Policy makers are now becoming more optimistic about the outlook for the U.S.