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Quick Method for Determining the Demographic Destiny of Any Group

May 27, 2020 26 comments

Here is one of those posts which I started writing years ago but did not finish till today, because it was.. well.. so short. Yes, one of the two reasons I kept delaying its publication was my inability to find something extra or deeply significant about the basic concept. The other being that this post will almost certainly attract some traditional and socially CONservative types- a group that I don’t care about.. to put it mildly.

So without further ado, here is how you determine whether any group (racial, ethnic, economic, religious etc) will grow or shrink in the near future. Ready.. if the median age of first birth in women of said group is under 26, then it has a bright demographic future. If the median age of first birth in women is over 28, that group is headed for a rapidly shrinking demographic future.

But wait.. there is more. The father’s age is equally important. Groups where the father’s age at time of birth of his first child is under 30 are expanding. Conversely, groups where the father’s age at time of first child’s birth is over 30 are aging and contracting. The above two observations hold regardless of factors such as historical era, race, ethnicity, religion, culture etc.

Confused? Let me explain the concept with a few examples and also tell you how I first stumbled on this observation. Looking back at my ancestors, I realized something peculiar about changes in number of children per woman. While both sides of my family tree were always well off, the number of kids per women (fertility rate) dropped sharply after the 1940s. This occurred irrespective of level of education for women or whether they had jobs outside the house.

The point I am trying to make is that the drop in fertility had nothing to do with ability to afford having more kids. Sure.. medical developments after 1940 ensured that almost all kids born to parents who can afford them will live to adulthood and beyond. But then again, the majority of kids born to my ancestors in previous eras made it to adulthood.. so survival of genetic legacy was unlikely to be a consideration.

So what was going on? Well.. while overhearing conversations among the older members of my family I realized that around that time, the average age of marriage of women went up rather steeply- from late teens to early 20s. We can certainly debate the social, economic and cultural shifts which caused that change- but it does not matter, because the outcome does not change. Years later, I noticed a very similar pattern when looking at chronological demographic data for countries such as UK and France.

By then, I had also noticed something else. The median number of children per woman drops below 2 once the age of having first child for women exceeded 28. Also, this observation holds regardless of country or social class. While this shift first occurred in the more “educated” and moneyed classes of every country, it has since spread much further- especially in westernized countries. The most curious part of this shift is that it has little to do with ability to financially support more children. And it gets even weirder..

While some of you might think that the correlation of male age at birth of first child with fertility rates is simply an artifact of men being a few years older than women in most marriages or relationships, it is a much more complicated than that. See.. men who haven’t had kids by 30 are much less likely to seek relationships where they want to have them. Moreover, even if they have kids after 30, it is seldom more than two- and usually one or one.

Now I am sure some of you will tell me about counterexamples they know in person. To that I say.. sure.. but I am talking about the correlation of parental age with average and median number of children. I am sure that somebody like a sports star, famous rapper, movie celebrity or somebody that is very interested in having many kids might have more. But they are the minority and face it.. very few people have a half-dozen or more kids.

To summarize, the total number of kids a woman has starts dropping sharply once her age at birth of first child is over 22, approaches replacement (IFR ~ 2) if her age is between 24-26 and goes below replacement (IFR < 2) once her age exceeds 28. As far as men are concerned, those who haven't become first-time fathers by 30 are unlikely to have more than two- usually one or zero. This occurs regardless of their financial ability to support more children.

I am sure that many of you will have a lot to say about my observations and potential reasons behind these socio-economic-cultural shifts.

What do you think? Comments?