September 8, 2013
to be posted on

25 St James St. sw1a 1hg
London, UK 

This is just a thank you note.  I have recently seen a couple of articles from you (Macro Mating ECCONOMIST vol. 408 no. 8853 September 14, 2013 page 36 and Buttonwood’s Notebook under Demographics online at  Of course I shall post this letter as I do all relevant correspondence when I get permission. 

My own obsession is demographics.  I regard its importance as being supreme, and you have long been my best source of numbers – without which I am nothing.  Of course we have a fundamental difference.  You see demographics as being the result of economic forces.  I see it as being independent of such sources.  For instance on my web site you would see a reference to a Danish study that points out that once issues of consanguinity are accounted for, education and income in Denmark have absolutely no effect on family size at all.  And there is a large amount of supporting evidence.  But just because we are looking at things from a different perspective (and I am sure you believe you have evidence also) does not mean you are not valuable to me. 

The Buttonwood article describes work by somebody who is predicting a veritable baby boom, nay the greatest baby boom of all time.  All the rich countries will be so flooded with young people that our budgets will all be in the black and our survival will extend into the dim reaches of the future.  Sure.  Personally I don’t think we need more people.  Why anybody with something of value, say citizenship in a nice country, would ever give it away or even sell a tiny amount of it for less than market price baffles me, but I am no economist.  But it’s nice for somebody to point out the upside of healthy fertility.  Me, I concentrate on the down side of infertility. 

The article cited takes as its first assumption that since in the developed world older women are having the babies, that this will always be true.  The researcher snatches at a blip in the birth rate among young women (I suspect it is among immigrants) and, assuming older women have more children and always will, does some arithmetical handsprings and conjures up his boom.  Also he demonstrates with satisfaction that educated women are having more babies; well and good and I suppose this is also immigration.  A very high proportion of our best educated are foreign born.

The printed article takes a more stately position and predicts a birth rate of 1.9 for a very long time, placing us in a state of genteel decline, which strikes me as splendid.  Only I don’t see that it’s possible. 

If you look at (which used to be quite nice but I now find the print almost unreadable) and follow birth rates plotted against age at first marriage as a surrogate for age at first child, following the plot over time, you will see a clear pattern.  Age of marriage and fertility bounce around since the first available statistics and then – at a moment that seems to be specific to each country – fertility falls and then levels off below replacement and immediately age at first marriage starts to rise.  It rises and never falls.  In fact it accelerates. 

We all know that just because B follows A does not mean that A caused B.  But if B always follows A with exactly the same timing then one must assume that there is a causal connection.  In this case there must be a common cause.  And the cause must be related to consanguinity since the Danish study has ruled out everything else. 

It doesn’t really matter to a first approximation what the cause is.  The clear fact is that it cannot go on forever.  And the age in some countries has reached the point where it cannot go up much farther before fertility again crashes.  And of course fertility cannot increase even if age at first marriage does not change because the ladies, even with modern medicine, are near the limits of their physiology.

I dare say that the blip in fertility among younger women will pull age at first child down a bit, but they are probably a different population.  To me a country is its population.  Its institutions are a mere convenience.  I know that this is not the only view.

So doom and gloom, doom and gloom.  But I do want to thank you for your interest.  Keep the good numbers coming.  Once we really know what’s going on and once we finally get at the cause, there is perhaps a chance to do something about it.  I don’t know what.  But I do no that nobody has ever tried it from the consanguinity angle and all attempts from the economic angle have failed.


M. Linton Herbert MD

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