Wikipedia: If the economy continues moving at the same rate,China should overtake Japan as second in 2012 and should replace the U.S.A as the world's largest economy & superpower on earth in 2030,meaning that the U.S.A will have been the world's superpower for [90years].Great Britain was the world's biggest economy & superpower,they replaced China from Mar1736 till Nov1940 [204years]. China & India was the world's richest nation & superpower from 2500BC till March1736.