China's economy will overtake US to become the biggest in world in next four years, according to Paris-based think-tank Organisation for Economic Co-operation & Development (OECD).

OECD said China's economy would become bigger than the combined economies of the eurozone nations by the end of current fiscal, and would surpass the US economy by the end of 2016.

By the year of 2025, the combined gross domestic product of China and India would be bigger than that of combined gross domestic product of Canada, Germany, France, Italy, Japan, the UK, and the US.

Speaking about the estimates, OECD senior economist Asa Johansson said, "It is quite a shift in the balance of economic power we are going to see in the future."

However, the think-tank acknowledged that it ignored possible risks like unsustainable use of natural resources and disorderly debt defaults.

The international think-tank also predicted that global gross domestic product would grow by 3 per cent per year over the next five decades, but it admitted that they would be huge variations among various countries and regions.

Inequalities will continue, though people in the poorest nations will see their income more than quadruple by the year of 2060, with Chinese and Indians seeing a more than a seven-time hike in the income.