According to the Knight Frank Wealth Report 2012, China will overtake the United States to become the world's largest economy by 2020, but by 2050, India will surpass both. 

The Knight Frank Wealth Report 2012 predicts which nations will comprise the world's top-ten economies in 2050, in terms of GDP. The report is published Knight Frank, a London-based independent global residential and commercial property consultancy, in partnership with Citi Private Bank, Citigroup's wealth management services arm for ultra high net worth individuals, law firms, and institutional investors. 

The report describes historical trends in the GDP growth of the world's largest economies up until 2010,  and it projects the growth of the same up until 2050.

London School of Economics professor Danny Quah forecasts that by 2050, the world's economic centre of gravity, a theoretical measure of the focal point of global economic activity based on GDP, will have shifted eastwards to lie somewhere between China and India, the report said. Professor Quah calculated that in 1980, it was in the middle of the Atlantic.

Citi research shows that while China and India are likely to grow rapidly over the next 40 years, there are other key countries with promising chances for growth that do not necessarily match the traditional assumptions about where future growth will emanate from, it added.

Click on Start to have a look at the top ten economies of the world and their projected GDPs in 2050.