In 1997, economists at the International Monetary Fund pointed out that China’s economy was growing so fast it might be bigger than the US economy by 2017. That didn’t happen. China’s economy did go gangbusters, however, and its population of more than 1 billion people seemed to assure it would eventually become the world’s biggest market. In 2010, Goldman Sachs estimated that China’s economy could overtake America’s as the world’s largest by 2030. The Economist was bolder, predicting China would become the world’s largest economy by 2019. The shift, whenever it came, would signal that a new economic superpower was...