A Theory of Shown Family Size

Bryan Caplan had a great post last week combining statistics, biology, and parenting to lead to the conclusion that weird people should have more kids.  First, the statistics. If there is a zero correlation between parental and child traits then your child is as likely to be as similar to you as is a stranger. If the correlation between parent and child traits is greater than zero then you are more likely to be like your child than a stranger but only if you yourself are not normal. Here is Bryan:

Take a look:
 

		Parent-Child Correlation
		r= 0		r=.5
	You	Stranger	Child	Stranger	Child
Percentile/ Expected Percentile	50th	50th	50th	50th	50th
	95th	50th	50th	50th	80th
	99.99th	50th	50th	50th	95th

Notice that regardless of the value of r, normal people can expect to be like their kids.  But that's not saying much, because normal people can expect to be like any random person they meet!  The story's very different for weirdos.  By definition, weirdos never have much in common with random strangers.  With a zero parent-child correlation, weirdos will feel equally alienated from their children.  As the parent-child correlation rises, however, weirdos' incompatibility with strangers stays the same, but their expected compatibility with their children gets stronger and stronger.

Now let's look at these facts like a mad economist.  There are two ways to surround yourself with people like you.  One is to meet them; the other is to make them.  If you're average, meeting people like yourself is easy; people like you are everywhere.  If you're weird, though, meeting people like yourself is hard; people like you are few and far between.  But fortunately, as the parent-child correlation rises, weirdos' odds of making people like themselves get better and better.

...The lesson: As your weirdness increases, so does your incentive to have kids.  If you like football and American Idol, you're never really alone.  You don't need to build a Xanadu for yourself.  But if you're a lonely misfit, oddball, freak, or weirdo, then find a like-minded spouse and make new life together.  Let the normals laugh at you.  You'll have each other.

via marginalrevolution.com

Apologies to Alex Tabarrok for lifting his entire post, but I couldn't find a way to excerpt it that would do it justice. Let me just say that if you read only one blog, it should be Rhymes With Clown. If you read a second, it should be Marginal Revolution.

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