Global markets continued a rocky start to 2016 on Thursday when China’s key stock benchmark, the CSI300, nosedived 7.2 percent after just 30 minutes of trading, triggering a halt for the remainder of the day. It was the shortest trading day in the market’s 25-year history, according to The Wall Street Journal, and the second shutdown this week. In New York early Thursday, Dow Jones Industrial Average futures pointed to a 300-plus point drop at its 9:30 a.m. open. The benchmark Shanghai Composite index also dropped 7.3 percent while the tech-focused Shenzhen Composite also fell 8.3 percent before trading was halted. Recent moves to weaken the yuan have stoked fears that the world’s second largest economy is slowing more than expected.