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.