Wednesday, July 26, 2006

The Effect of Kids on Parents

The recent discussion of the odd distribution of Congressional birth signs reminded me of another odd fact about politicians -- they (well, US Presidents at least) have way more sons than daughters.

Several years ago, my friend Keith Chen mentioned that some evolutionary biologists he knew were trying to understand the bizarre finding that the men who have served as President of the United States had substantially more sons than daughters. As evolutionary biologists, they, naturally, focused on figuring out if alpha-males somehow had different sperm that led them to produce more males (and figuring out why dominant males evolved this way). Keith and I, being economists, felt that the biologists were likely asking the wrong question. Rather than asking what about the alpha-male led them to have more sons, why not ask what about having a son might affect the odds of becoming the alpha-male (or at least the President)?

We developed two main hypotheses for the finding. First, the electorate may have preferred voting candidates with sons. Second, having sons might motivate fathers to work harder and achieve more. This might occur if sons cost more to raise (and one can imagine that might have been true in a period where sons were more likely to go to school), if fathers care more that their sons are proud of them, or (as the Dahl and Moretti evidence that daughters cause divorce might suggest) sons improve marriage quality allowing fathers to devote more energy to work (alternatively fathers may work more to compensate their wives for providing them something they value).

For reasons that I no longer remember, we chose to investigate the second. Given that child gender is exogenous, we planned to compare changes in post-birth labor market outcomes for men who had sons to men who had daughters. Unfortunately for us, just as we were starting our work, I randomly discovered a working paper (that would eventually be published in the AER -- ouch!) by Shelly Lundberg and Elina Rose that did exactly what we were going to do. Consistent with our hypothesis, Lundberg and Rose find that fathers who have sons increase their labor supply by more and earn higher wages than fathers who have daughters:

Our most notable results relate to the effects of child gender on men's labor market outcomes. Sons increase men's annual hours of work and wage rates significantly more than do daughters. Fathers of both cohorts respond differently to sons and daughters, though the gender effects are more pronounced in the hours worked of the late cohort and the hourly wage rates of the early cohort. We find little evidence of an effect of child gender on the labor market outcomes of mothers, and are unable to explain our results in terms of differences in the expected pecuniary returns to boys and girls in the United States. Our results are consistent with a model in which the gender composition of a couple's offspring affects the returns to marriage, and this has implications for future research.
I, much like Lundberg and Rose, am not sure what is going on, but the combination of the effect of sons on divorce and men's labor market outcome certainly merits further research -- specifically into what's causing these effects and whether or not they have changed in recent years.

In order to balance out (a little) these results (and perhaps suggest another possible explanation for them), let me also direct you to an interesting paper by Ebonya Washington that finds that Congressmen who have daughters are more supportive of women's issues (a very similar result to the roommates paper discussed previously):

Economists have long concerned themselves with environmental influences, such as neighborhood, peers and family on individual's beliefs and behaviors. However, the impact of children on parents' behavior has been little studied. Parenting daughters, psychologists have shown, increases feminist sympathies. I test the hypothesis that children, much like neighbors or peers, can influence adult behavior. My laboratory is the United States congress. I demonstrate that conditional on total number of children, each daughter increases a congress person's propensity to vote liberally on reproductive rights issues. The effect is better explained by a shift in parental preferences, than by a shift in knowledge of constituency views or in the cost of living under a conservative reproductive rights regime. The result demonstrates not only the relevance of child to parent behavioral influence, but also the importance of personal ideoloa legislatorslator's voting decisions as it is not explained away by voter preferences.

I think this is good, although if having daughters hurts you at the polls ...

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