When it comes to crime, economists focus on deterrence. Deterrence works but it’s not the only thing that works. Simple things like better street lighting can reduce crime as can high-quality early education or psychological interventions such as cognitive behavioral therapy. The sociological literature has emphasized that crime is about preferences as well as constraints. Life-events or turning points such as marriage and childbirth, for example, can greatly change crime preferences. The sociological literature is mostly from case studies but in an excellent new paper, Family Formation and Crime, Maxim Massenkoff and Evan Rose (both on the job market from Berkeley) demonstrate these insights in a huge dataset.

A big part of what makes their paper compelling is that almost all of the results are blindingly clear in the raw data or using simple analysis. Here, for example, is the crime rate for women (drug, DUI, economic, or property destruction crimes) in the years before pregnancy, during pregnancy (between the red dotted lines) and after birth. Crime rates fall dramatically with pregnancy and in the three years after birth they are 50% lower on average than in the years before pregnancy.

Pregnancy imposes some physical limits on women but the effects are also very large for men whose crime rates fall by 25-30% during pregnancy of their partner and continue at that lower rate for years afterwards. Keep in mind that in our paper on three strikes, Helland and I found that the prospect of an additional twenty years to life (!) reduce criminal recidivism by just ~17%, so the effect of pregnancy is astoundingly large.

It’s not obvious what the policy implications are. Have children at a younger age doesn’t sound quite right, although in an analysis on teen births Massenkoff and Rose do indeed show that whatever the costs of teen pregnancy there are some offsetting benefits in reduced crime of the parents. More generally, however, there are policy implication if we think beyond the immediate results. First, these results show that crime isn’t simply a product of family background, poverty and neglect. Crime is a choice.

In Doing the Best I Can: Fatherhood in the Inner City, Edin and Nelson relay the following anecdote (quoted in Massenkoff and Rose):

Upon hearing the news that the woman they are “with” is expecting, men such as Byron are suddenly transformed. This part-time cab driver and sometime weed dealer almost immediately secured a city job in the sanitation department (p. 36).

Byron chose to change and he did so based on the rational expectation of a future event. Massnekoff’s and Rose show that these choices are common.

Instead of thinking of these results as being about pregnancy and marriage we should ask what is it about pregnancy and marriage that makes people reduce crime? Love, responsibility and long-run thinking are all at play. In economic terms, pregnancy reduces discount rates and gives men and women a reason to invest in human capital and work for the future. Children and marriage play a large role in socializing and “civilizing” both men and women but they surely can’t be the only such factors. Indeed, although men and women on average reduce their crime rates dramatically on pregnancy this is mostly coming from men and women who had high rates to begin with–there are plenty of men and women who don’t much reduce their crime rates on pregnancy because they were already low–in a way, these men and women were pre-socialized so how do we extend the benefits of pregnancy to the expectation of pregnancy or how can we widen the effect to other factors that can also civilize?