Check out how the world's largest and fastest growing economies change over time from 2008 up to 2020. China is growing by leaps and bounds while the front runner the United States are steadily growing. By 2020 US GDP is estimated to grow to $22.5 trillion while China is estimated to grow to $16.2 trillion. At 3rd will be Japan at $4.9 trillion, 4th is Germany at $4.1.
Check out the CNN Graphics here
Estimated; Data: IMF, World Economic Outlook; Updated Feb. 11, 2016