The China Threat

Economy: When will China become the world's largest economy? Goldman Sachs estimates that it will happen by 2027. But, using a forecast based on purchasing power parity, The Conference Board, a business-research group, predicts it could happen as early as next year since goods and services are cheaper in China.

Threat Level: High  While social instability might derail China's growth, financially speaking this is China's century. However, the U.S. will continue to benefit from Chinese growth, and even when China's economy surpasses that of the U.S., Americans will still have much higher per capita income.