Gross domestic product in the United States is projected to hit $15.6 trillion in 2012, making its economy the largest on earth.
The quickly expanding Chinese economy is the world's second largest, having recently surpassed Japan. China has a projected GDP of $7.9 trillion in 2012 -- just more than half that of the United States. But even with annual growth rates of 7% to 10%, it will be decades before China's production approaches that of the United States.
Related: World's largest economies
Of course, the U.S. economy faces notable challenges. The country has been slow to recover from the 2008 global financial crisis, the labor market remains weak and the U.S. housing sector will take years to recover from its recent bubble.
