China’s transformation is trickling even into the poor interior, dragging all 1.3 billion people into the world economy. When historians look back on our time, I think they’ll focus on the resurgence of China after 500 years of weakness — and the way America was oblivious as this happened. For most of human history, China was the world’s largest economy and most advanced civilization. Then it stagnated after about 1450, but some estimates are that even as late as 1820 China amounted to 32% of the world’s G.D.P. — and then it utterly collapsed. Now, with a billion people emerging from subsistence, China is on course eventually to recover its traditional pre-eminence.