China has overtaken Japan to become the world's second-largest economy after the United States, the country's chief currency regulator said in remarks published on Friday. The economy expanded 11.1 percent in the first half of 2010, compared with a year earlier, and is likely to log growth of more than 9 percent for the whole year, according to Yi Gang, head of the State Administration of Foreign Exchange. "China, in fact, is now already the world's second-largest economy," he said in an interview posted on his agency's website.