China poised to pass US as world’s biggest economy

This prediction is based on estimates of the real cost of living, known as purchasing power parity or PPPs which according to this FT article "are recognised as the best way to compare the size of economies rather than using volatile exchange rates". PPP theory takes into account the cost of living in individual countries and the International Comparison Program, the organisation who have come up with the research causing all the headlines have found that money goes much further in poorer countries than it previously thought. Aside from China about to take the top spot away from the US (a place the US has occupied since 1872) "the figures revolutionise the picture of the world’s economic landscape, boosting the importance of large middle-income countries. India becomes the third-largest economy having previously been in tenth place."