Still, several readers came up with other ways to explain the facts. A lot of their stories were rooted in evolutionary biology, e.g., "a boy is a better genetic investment because boys can have more progeny than girls." Unfortunately, that doesn't work. For every boy with more than the average number of offspring, there's another with less than the average number. Boys are likelier than girls to generate 20 children, but they're also likelier to generate zero.
The most creative evolutionary biology explanation comes from reader Todd Peters: Boys with low self-esteem become withdrawn and unattractive; girls with low self-esteem become promiscuous. So, if you want lots of grandchildren, you've got to raise the self-esteem of your sons (by staying married) and lower the self-esteem of your daughters (by getting divorced).
Ooookay. But let's end on a serious note, with a whole new way of looking at this—the way I wish I'd thought of to begin with. Suppose parents believe that inherited wealth is more important to a boy than to a girl—either because wealth gives boys a bigger advantage in the mating competition or because boys are more likely to do something entrepreneurial. Then parents of boys will try harder than parents of girls to preserve their wealth. In particular: 1) Parents of boys will avoid divorce, because divorce is costly; and 2) parents of boys will have fewer children, because extra children dilute the inheritance.
That could explain the divorce statistics and explain why parents of boys are less likely to try for more children. So, here's a nice theory that fits all the facts and doesn't rely on a preference for boys.
Finally, a lot of readers asked me about my own preferences. I cannot imagine why they're interested. If I were reporting on national employment trends, would you want to know my personal employment history? But for the record, I'm pleased to say that I always wanted a girl, I got the girl I wanted, and so far she's perfect. Ask me again next month after she starts driving.