In 2009, China’s economy was only a fourth of the size of the trillion dollar U.S. economy. Given current growth rates in both US and China, China’s output will exceed America’s somewhere in mid ’20s. But a richer China doesn’t mean America will be poorer! The Chinese population is so much bigger than America’s, average Chinese living standards may lag far behind. Average American incomes will still be twice Chinese incomes in 2050 (Goldman Sachs). Also the PPP figures indicate that, while the size of China’s economy is substantial, its living standards fall far below those of the U.S. and other Western countries.  This is exactly where previous hegemonic predictions have gone wrong. In the sixties economist Samuelson stated that GNP in the USSR was about half that in the US but the Soviet Union was growing faster.  As a result, one could comfortably forecast that Soviet GNP would exceed that of the United States by as early as 1984 in any event Soviet GNP would greatly catch-up to US GNP.  A poor forecast. So who knows if their will be a China in the next four decades?