Wednesday, 12 December 2012

Are Sons or Daughters Better for Marriages?

Since yesterday I’ve been pondering an interesting stat I read - apparently in a survey of 3 million people undertaken in America, a couple is 5% more likely to divorce if they have a girl than if they have a boy.

The first thing that springs to mind is to wonder whether this suggests women who have daughters don't feel such an intense need to stay married, or whether fathers prefer staying in wedlock for sons.  Then I wonder whether sons improve the quality of the marriage, or whether they exacerbate the travails of getting divorced. Or it could be that daughters either exacerbate the travails of a troubled marriage, or that they improve the prospect of separation.  Having thought about the statistic for a bit, I have further ideas – but first I will mention a particular objection you might have (and someone actually did have) – that 5% is not a very significant percentage to prove causation as well as correlation.

Given that the survey had a sample space of 3 million, it’s clear that 5% is very significant. Here's a simple illustration showing why it proves causation as well as correlation. If you gave 3 million people one coin each and asked them to toss it, and then separated them into two groups - those that landed heads and those that landed tails - you'd get two statistically identical groups in all the ways that you'd want to measure the average - average annual wage, height, weight, intelligence, and all manner of things.

The reason being; what you have is the mathematical law of large numbers; a huge sample space (the group population) and a random component (the coin toss). Suppose next we take the mathematical law of large numbers and try it on parents, where the sample group is divided according to last born child's gender. Once again we have the same number sample size, meaning we have two statistically identical groups in all the ways that you'd want to measure, and the gender of the last born as the random component (that's as random as the coin toss). Since every other variable returns two statistically identical groups regarding the average, the 5% difference has to be down to the last born child's gender.

Now back to the significance of the 5% statistic.  The first thing I noticed was that although the figure was 5% in America, it was higher in countries that place a greater premium on sons – higher in Mexico than America, even higher in Kenya, and even higher still in China (a country notorious for favouring male progeny).

As well as the 5% divorce statistic, it also proved to be the case that divorced women with daughters are much less likely to get married again than divorced women with sons.  This might suggest that daughters are more inimical to a successful 2nd marriage market than sons – but that seems to be a rational decision from mothers protecting their daughters, because a new stepfather is a new risk by being a potential predator from which the daughters’ sexual innocence needs protecting (even if most stepfathers don’t turn out to be a threat). 

So, if a couple is 5% more likely to divorce if they have a girl than if they have a boy, then do boys help sustain marriages or do girls help with divorces?  Statistically boys develop their careers and end up being better economic providers for their parents' old age – so this might explain why the percentage is so much higher in China than in America. I also think there is something in the idea that daughters improve the prospect of separation for mothers.  Furthermore, if the notion of passing on the family name has any analogue to passing of genes (which it might have) then that might be another factor that keeps men in marriages with sons. 

Here’s another thing to consider. Given that boys bring more anti-social stigmas back into the household, this might suggest the mother-son single life is harder than the mother-daughter single life - which may be a factor in the above stats, and may suggest mothers prefer having fathers around with boys. Moreover, I suspect a corollary of this is that mother-daughter bond is strong to the extent that a life together without a husband strikes the mother as being more secure and manageable.  I became more strongly drawn to this hypothesis when I found out that nearly three quarters of all divorces involve the wife leaving the husband, which suggests that men might not be staying married for the sake of their sons or daughters, but that significantly more women feel more confident leaving their partners when they have a son than when they have a daughter.  Even so, a man with a greater incentive to stick around for a son probably will be a man who tries harder at his marriage.  This could also explain a further stat – it emerged that parents of daughters are significantly more likely to try for another child than parents of sons – and this feeling also increased upwards from America through to China as it did previously, which seems to support the view that sons are preferred by men. 

I did visit one webpage in which a clinical psychologist (I didn’t register her name) who had done work with adoption agencies tried to rebut the idea of preferences for boys by showing in her findings that the records of adoption agencies show a higher demand for girls than boys.  But I think the psychologist has her reasoning backwards; in a world where parents have a preference for boys over girls, it stands to reason that couples looking to adopt will more likely choose a girl.  The distinction may not be significant enough to have a major effect – but it doesn’t have to be huge, just a bit will do.  As long as probability is considered, it will always be slightly preferable to adopt a girl, because if boys are preferred by their natural parents then boys put up for adoption are more likely than girls to have a personality less conducive to preference. 

In marginal or nominal circumstances, sometimes a more extreme analogy can give clearer exhibition to the point – so I’ll give you one. Imagine a world in which 99 out of every 100 people preferred to own dogs over cats.  Suppose you visit an animal sanctuary looking for a pet, and your choice is between a quantity of dogs and cats that have previously been pets of someone else.  In a world with a 99/100 preference for dogs, you’re going to be much more put off the dogs on offer because you’ll assume that the previous owners gave up their dogs because they weren’t easy to have as pets.  This is almost certainly the same reason why records of adoption agencies show a higher demand for girls than boys.  Their rationale won’t always be right for couples looking to adopt, but it has a higher probability of providing a more favourable outcome – and that’s what matters most to people’s instincts.