How will it feel when China becomes the world’s largest economy? We may find out quite soon. A few weeks ago, the International Monetary Fund issued a report that suggested China would be number one within five years.

The projection that the Chinese economy will be larger than that of the US by 2016 included adjustments for the domestic purchasing power of the two countries’ currencies. Some regard this interpretation of IMF data as a dubious move that artificially boosts the size of the Chinese economy. But even using real exchange rates does not defer the day when America is knocked off its perch by very much. A projection by The Economist, made just before Christmas, foresaw China becoming number one in 2019.

The ascent of China will change ideas of what it means to be a superpower. Over the course of the American century, the world has got used to the idea that the world’s largest economy was also the world’s most obviously affluent nation. The world’s biggest economy housed the world’s richest people.