The world population is aging fast, but is still younger than we tend to think
It's not so obvious how old a 60-year-old is. Ask most 60-year-olds these days and they'll say they still feel pretty young, since they're healthy and expect many active years to come. In 1900, though, a 60-year-old was, well, old.
This simple fact has big ramifications for demographers. Demographers have long known that on average people are getting older all around the world, and they have worked to assess the likely social impacts of that aging. For example, relatively few young people are around to support old people's pensions. But increased longevity counteracts those impacts by making people of any age in effect younger than they used to be, for example increasing the number of years they are capable of working. So it has been hard to assess how big the impact of an aging population is likely to be.
A trio of demographers has now developed new measures of age to fill this gap. Instead of analyzing people's chronological age, they've measured the number o