I think there are other significant forces at work as well. Well, they are at work when birth control is available and social/religious taboos do not prevent them.
Most of the world exists in different stages of a demographic transition from high infant mortality to low infant mortality. Some countries are completely through the transition already. In those countries, the average fertility is well below 2 children per woman. In the 25 countries of the EU, it is at 1.5 on average. Japan is at 1.3. North America is 2.
The “cost” of having too few children is no free labor and no old age security. The “Cost” of having too many children is a tremendous burden and hardship on the family itself to maintain its own level of living. From these forces comes a balance that seeks for the unit to perpetuate itself, plus a little bit more or less. It is a natural state of mankind and can be shown before and after the demographic transition brought about by the current causes of population increases.
I guess what I am trying to say is that within 1 or 2 generations, with no intervention by man or government, each society has, and I believe will continue to, self adjust it’s own birthrate. I personally think it will end up somewhere between 9 and 10 billion, and decline from there naturally.
There are some
animations on this website that show some of what I mean.