While this is affecting every country and region – even sub-Saharan Africa is now seeing a very fast rise in its proportion of seniors – some countries are being hit very hard. While 12 per cent of Chinese are now over 60, in two decades, there will be more than 28 per cent. Brazil faces a similar blow. It will be very difficult for countries that are only just emerging from poverty to suddenly face huge elder-care costs.

Peak people will be an age when jobs compete for workers rather than vice versa. The cheapest labour will vanish. We’re already seeing this: Because China is aging very fast, its dwindling working-age population is turning down the lowest-paid jobs and pushing up the minimum wage sharply, as well as the once-minimal costs of social services: Stuff from China will stop being cheap, because the Chinese aren’t young.

This can have larger consequences than we imagine. For example, the United States appeared to be escaping the worst of the aging trend because it has an unusually high fertility rate (averaging almost 2.1 children per family, half a child more than Canada and Europe). Most analysts assumed that this was the result of American religion or prosperity. But an important new study by economists Moshe Hazan and Hosny Zoabi has found that the real reason for larger families is the unusually large supply of low-cost babysitters and child-care workers in the U.S. – mainly due to immigration, much of it “illegal,” from Latin America. But those Central American countries and Mexico are themselves aging fast, which will soon choke off that cheap labour supply and drive up the cost of having extra kids – which will cause the U.S. to become less fertile and more elderly.