population growth is a bit scary. World population only reached 1 billion around 1840 and it took until around 1940 to reach 2 billion. Since then we hit 4 billion in the 1970s, 5 billion in the 1980s and 6 billion in the late 1990s.
It's mildly reassuring to at least know that the rate of growth is now falling, but estimates of the level at which the global population will reach a maximum are in the range of 11-13 billion. Virtually all future growth is predicted to occur in the developing world.
Sorry to sound like a textbook, but I teach this stuff
Matt