The UN recently revised its population projections. Some 6.3 billion people now live on Earth. If fertility rates in relatively poor countries continue to follow the trends set by today's relatively rich countries, we are within shouting distance of the world's maximum population-9-10 billion-to be reached in 2050-2100.
But population may well decline thereafter. Literate, well-educated women with many social and economic options in today's rich countries have pulled fertility below the natural replacement rate. The problem is not that such women on average want fewer than two children; in fact, on average they wish to have a bit more than two. But because many of them delay childbearing until their thirties, actual fertility falls short of what they desire.
A world population that peaks at 9-10 billion is not one in which we have to worry about Parson Malthus, the English 19th century economist who prophesied a future in which people multiply faster than the resources needed to sustain them and hence starve to death by the millions. Indeed, it comes as somewhat of a shock to realize that the age of the population explosion may be coming to an end.
Just thirty years ago, people like Stanford University's Paul Ehrlich were telling us that the Malthusian Angel of Death was at the door. They assured us that it was too late to stop the famines that would kill hundreds of millions in the Indian subcontinent, and that humanity's destiny in the 21st century was one of war and struggle for the resources to feed national populations an extra crust of bread.