It's mainly a matter of choices and what makes us happy. Today we are more focused on material things and the family unit is suffering. Years ago big families often with very few resources was the norm and people were probably happier. We didn't hear of major massacres every second week. We were busier with activities directly necessary for living which probably kept us physically and mentally in better shape.
I think it is the exponential growth of the population that has taken us by surprise in the last sixty years. Up until then having a baseball team wasn't that big a deal, for everybody. The reason China has taken the step of going to a one child policy is that the realization of overpopulation has hit them first/hardest.
The Chinese education system went through a huge expansion and made the need for change an obvious thing. Overpopulation is relative to the availability of the basics of life. Our agriculture has produced far better than could have been imagined 60 years ago, but that progress has been made by using fossil fuels that we are now realizing we can't afford. A one child policy, whether official or voluntary would help to get us past the shortage of food that is going to be coming down the pipes at us over the next twenty years. More to the point a human right to a non-sectarian education should be our priority wrt population control.