|
In most third world countries, the only retirement plan for the poor is to have children to support you in old age. People breed early and often, especially when you can't count on having all of your children survive to adulthood.
As a society grows wealthier and better educated, parents have fewer children, have children later in their lives, and spend far more time on the upbringing of each child. In Japan, most of Eastern Europe, and some other wealthy countries, people have too few children to sustain the current population. Either the difference is made up by immigration, or the population declines.
Aside from sub-saharan Africa and maybe parts of Asia, I'm sure there will be no population crisis, as the pace of carrying capacity improvements will exceed population growth, right up until population growth stalls.
|