If global fertility rate becomes that like Japan, we'll have a halving of the population every generation. This leads to a global population of 78 million after 10 generations. Also a miserable population because each person needs to support two elderly people while before it was two people supporting one elderly. That's a 4x increase in work.
But what if we adjust the figure to take into account those percent Japanese who want children but cannot afford them? When the population begins to "extinct" because of those who can but do not want to reproduce, those who want to but cannot now will be able to do it.
