Assuming that the Chinese and US economies grow, respectively, by 8% and 3% in real terms, that China’s inflation rate is 3.6% and America’s is 2% (the averages of the last decade), and that the renminbi appreciates against the dollar by 3% per year (the average of the last six years), China would become the world’s largest economy by 2021. By that time, both countries’ GDP will be about $24 trillion, perhaps triple the size of the third largest economy, either Japan or Germany.