It’s official: China has overtaken the U.S. as the world’s largest economy. The International Monetary Fund estimates China’s economy is $17.6 trillion, just ahead of the U.S. at $17.4 trillion. China gained quickly. It was just 2005 when China’s economy was half the size of the U.S.‘s, though by 2020, IMF says it will be 20% bigger. IMF is accounting for individual purchasing power, which means that, though salaries are still lower in China, that money buys more. By the end of this year, China will account for an estimated 16.48% of the world’s purchasing-power adjusted GDP, again ahead of the U.S. at 16.28%. Thanks, Obama. More…