Up until less than a hundred years ago the only way to make sure any of your kids survived was to have seven or eight of them. This has change dramatically in the developed countries and is on the way every else as well as standards of living increase.

Child births need to be at around 2.1 per woman if the population is to remain constant. Right now most developed countries are way below that.

https://en.m.wikipedia.org/wiki/List_of_sovereign_states_and...