BEIJING (AP) — China's stock market tumbled this week despite a massive government intervention aimed at halting a slide in prices that began last month. At its peak in early June, the Shanghai Composite Index had risen about 150 percent from late 2014. After dropping 30 percent over several weeks, government support measures calmed the market. But on Monday the sell-off resumed, with the Shanghai index suffering a drop of 8.5 percent, its biggest daily fall since February 2007. Here's what the sell-off means for China's economy and other countries.