Mother Jones on the last taboo - population:
"The United Nations projects that world population will stabilize at 9.1 billion in 2050. This prediction assumes a decline from the current average global fertility rate of 2.56 children per woman to 2.02 children per woman in the years between 2045 and 2050. But should mothers average half a child more in 2045, the world population will peak at 10.5 billion five years later. Half a child less, and it stabilizes at 8 billion. The difference in those projections—2.5 billion—is the total number of people alive on earth in 1950.