Just how much economic trouble is China in? To judge by global markets, a lot. In the first few weeks of the year, stock markets around the world plummeted, largely thanks to fears about China. The panic was triggered by an 11 percent plunge on the Shanghai stock exchange and by a small devaluation in the renminbi. Global investors—already skittish following the collapse of a Chinese equity-market bubble and a surprise currency devaluation last summer—took these latest moves as confirmation that the world's second-biggest economy was far weaker than its relatively rosy headline growth numbers suggested.