NEW YORK — Deepening worries about global economic growth, particularly in China, set off a rout in riskier assets including technology stocks, copper and crude oil Wednesday. U.S. retailers took a drubbing after Macy’s reported weaker sales.An unexpected drop in profits for Chinese tech giant Tencent surprised investors and added to some recent concerns about the health of China’s economy. Tencent, a gaming and messaging company, is the most valuable technology company in China.Earlier this week, reports on growth in factory output, consumer spending and retail sales in China were all slower than expected.Large technology companies including Alibaba and Baidu of China and U.S. tech giants including Facebook and Microsoft fell.Oil prices sank and copper plunged to its lowest price in a year as investors worried about the health of the global economy. The S&P 500 index had its biggest decline since late June while traditionally safe investments like bonds and high-dividend stocks rose.“This year we’ve seen slower growth. Everyone expected that,” said Kate Warne, an investment strategist for Edward Jones. “Over the last couple of months it looks like growth has been slower than everyone expected.”The S&P 500 slid 21.59 points, or 0.8 percent, to 2,818.37. Earlier it fell as much as 1.3 percent.The Dow Jones Industrial Average fell 137.51 points, or 0.5 percent, to 25,162.41. The Nasdaq composite dropped 96.78 points, or 1.2 percent, to 7,774.12. The Russell 2000 index of smaller-company stocks sank 21.91 points, or 1.3 percent, to 1,670.67.