Today I have been thinking about the future and some demographic challenges facing the world.

I now have a theory that falling birth rates are not connected to rising income / wealth, but are instead a consequence of rising life expectancies.

This is a statistical simplification and so any personal feelings or individual experience is irrelevant in this larger context.

Here goes…

Life expectancy fits the data much better than wealth. It’s why Japan went through japanification long before the richer USA.

I propose that many people do not really desire children until they consider their own mortality or frailty. Once your current age forces you to think about your own mortality you immediately think about children and who will be around you near the end. This is a natural thing to think about. It doesn’t really go away.

At the population level, as life expectancy has increased from 50 to 80, people have greatly delayed this train of thought until much later in life. For most people in the modern world, they never actually consider this train of thought during their years of high fertility.

This then assumes that people today mostly have children as an accident of sex, or because of the (significant) momentum of cultural norms and not really as a functional decision of self interest.

Birth rates aren’t going to 0.00 because there are lots of reasons to have children, but I think the fact that most couples of child bearing age can rationally assume they will live another 50+ years, they are not thinking about their mortality or frailty.

As a result… birth rates are falling everywhere, or rather everywhere that has a life expectancy that is double the female age of fertility.

I think this is a much more satisfying hypothesis about falling birth rates than the idea that richer people choose to not have children. That doesn’t really stack up for household income distributions within a society with a particular life expectancy.

And yes, I understand that life expectancy is also correlated strongly with income and wealth.

I just this this hypothesis is a more realistic fit. What do others think?

I understand this will be an emotional topic for some and not everyone is fortunate enough to realise their preferred choice regarding children. I think most couples have some level of compromise between partners and obviously some couples are just painfully unlucky.