Since humans started organizing into communities, the shape of any given society, broken into age groups and gender, has always resembled a pyramid: The largest age group has always been the youngest (0-4), and the oldest group (75+) has always been the smallest, with each age group in between falling in more or less a straight line, forming a triangle. But starting in 1975, The Economist explains, falling birth rates and rising lifespans have converted the triangle into a bell shape, or the profile of a temple at Angkor Wat.
The otherwise dry demographic data is really brought to life in the video below, and the really interesting (perhaps terrifying) shape-shift is projected to happen in the next 45 years. By 2060, the number of people 85 and above is set to mushroom by 281 percent, while the population of of people 60 to 79 is expected to double, adding 850 million — more than four times the growth of people 19 and younger, whose population will grow just 8 percent, by 200 million. The population pyramid will start to look like a column. If these World Bank projections prove accurate, human society will look very different, very soon. And you might well live to see it. --Peter Weber