November 16, 2012
to be posted on

Lee Kuan Yew
Care of People’s Action Party
Blk 57B, New Upper Changi Rd,
#01-1402, PCF Building, Singapore 463057   Tel : 65-6244 4600

Dear Minister:
I have just re read an article about the birth rate in Singapore (Banyan An Exercise in Fertility ECONOMIST vol. 396 no. 800 September 18, 2010 page 60)  The article is two years old and I understand you have since retired, but I imagine you still have an interest.  A superficial glance at recent statistics suggests a very low birth rate, around .78 babies a woman can expect over a lifetime.  I keep reading that as 1.78, which would be bad enough.  So it would appear that things have not improved. 

As with some other countries Singapore has made valiant efforts to encourage a healthy birth rate with financial incentives and persuasion.  As with other countries these have failed.  Normal prudence dictates that one must do the same as others are doing.  However when those measures fail it is occasionally necessary to learn from the mistakes of others. 

My own impression of the evidence is that a given couple will have a certain number of children, that this is a biological phenomenon and that no incentive, encouragement or law is going to have any great effect in shifting that up or down.  You cannot buy babies. 

Obviously some couples have more children than others.  The question is why.  As it turns out, this question has a scientific answer.  The number of children depends on the degree of consanguinity of the couple.  You can have too much and you can have too little just like everything else.  Here are some references for you.  The first (Human Fertility Increases with marital radius. Rodrigo Labouriau and António Amorim.  GENETICS volume 178 January 2008 page 603) found that once issues of consanguinity were taken into account – size of town and distance between birthplaces of the couple – education and income had absolutely no effect on fertility.  This first article showed inbreeding depression but no loss of fertility with fall in consanguinity out to the limits of the study.  This omission was corrected in a later article (Comment on “An Association Between the Kinship and Fertility of Human Couples,” Rodrigo Labouriau and António Amorim SCIENCE vol. 322, page 1634b December 12, 2008) and it was found that with greater marital radius fertility did decline.

Another team looked at consanguinity and fertility in Iceland.  (An Association between Kinship and Fertility of Human Couples Agnar Helgason et al. SCIENCE vol. 329 no. 5864 February 8, 2008 page 813 – 816)  The same relationship more or less held.  No decline in fertility was found with inbreeding in the first generation, although it did seem to be present in the second generation.  A recent article comparing rich Swedes with  poor Swedes (Low fertility increases descendant socioeconomic position but reduces long-term fitness in a modern post-industrial society doi: 10.1098/rspb.2012.1415
Proc. R. Soc. B 2012 279, 4342-4351 first published online 29 August 2012
Anna Goodman, Ilona Koupil and David W. Lawson), and I assume that rich people are less likely to marry cousins as are urban people, showed the same effect on children and grandchildren and – if I read it right – an even greater effect on great grandchildren. 

An older article (On the Regulation of Populations of Mammals, Birds, Fish and Insects, Richard M. Sibly, Daniel Barker, Michael C. Denham, Jim Hope and Mark Pagel SCIENCE vol. 309 July 22, 2005 page 609) shows that the same relationship is present in just about every complex animal. 

This is science, not politics.  Consanguinity determines fertility.  Nothing else is of sufficient consequence to be visible in the data. 

You would think that somebody would be desperate enough to abandon methods that have been proven not to work and try methods that science predicts would work.  That would be asking a lot, of course.  One could imagine a country offering a certain number of cash prizes to couples who married who were third cousins.  (That is about the sweet spot, the best for grandchildren, but I oversimplify.  A careful reading of the references is needed.  But maybe the plan doesn’t have to be perfect.)  The only stipulation would be that if the couple broke up they would have to give the money back.  They would also have to keep some government agency notified about their pregnancies and children. 

Within a year or two it would be obvious whether the scheme was working or not.

But such an idea would take a lot of thinking.  The obvious thing to do would be to get experts together and have them reach a consensus.  I can tell you what the consensus would be; they would reject it out of hand without evidence.  Remember, ordinary prudence is to do and think like everybody else, and that would determine their judgment. 

You are an expert of people.  I am not.  If you have any idea as to how one might proceed, let me know.  If I can be of any help, please let me know.


M. Linton Herbert MD 

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