Bryan Caplan  

The Modality of Monogamy

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After running last week's abortion regressions, I looked at the General Social Survey's histograms for reported numbers of sexual partners.  They're weird.  Here are the distributions of opposite-sex partners for men and women.

Figure 1: Men's Reported Lifetime Number of Opposite-Sex Partners
Figure 2: Women's Reported Number of Lifetime Opposite-Sex Partners

Notice: The most common number of lifetime partners for both genders is 1!  This is not an artifact of the binning, because the "1 partner" response is in its own bin. 

Of course, people could be lying.  But in what direction would they lie?  Conventional wisdom says that men overstate and women understate.  For men, then, the modal monogamy result is probably even stronger than it looks.  Furthermore, to overturn the modal monogamy result for women, we would have to imagine that women have markedly more partners than men claim to have.  Possible, but definitely weird if true.

What do you think?  Can monogamy truly be modal?  My guess is that the pattern is real.  It seems weird because people with lots of partners are vivid and memorable.  Think about how many popular adult t.v. characters are in the 21-100 or even 100+ bins!  The obvious explanation is that the media is desperately trying to pique and hold our interest. 

The latter observation may tempt you to blame the media.  It's easy to believe that the media amplifies our biases.  The root bias, though, is overestimating the frequency of the vivid and the memorable.

COMMENTS (6 to date)
Graham Peterson writes:

You find this distribution in every sex survey of different subpopulations, not just the GSS, and it's shape is stable over decades. The number of partners young people has not increased either.

Campus hookup culture hysteria (and hysteria about sexual promiscuity generally) is a result of people getting mad about changing dating rituals.

Over time, dating has become less and less public and sex more and more public. It used to be the reverse. The sexual "revolution in the 60s is part of a much longer trend.

Making sure that dating is very public and very extensive before sex makes sure that people make credible long term signals/investments with one another in order to ensure they'll be around for extended gestation and child rearing.

That is no longer necessary or desirable in a world with material abundance and reproductive technologies, but turns out that people nevertheless prefer fewer partners to more because people gain an enormous array of benefits from romantic relationships outside of sexual gratification.

walk this way writes:

This is randomized across all individuals above the age of 18 right? This doesn't genuinely capture "lifetime partners". Move forward 30 years and a lot of those 0s move into 1s, and a lot of those 1s move into 2s or 3s.

I don't think there's a way to adjust for this, given that generational change is what we're trying to measure; we'd have to assume something about the hypothesis.

walk this way writes:

I think other surveys show a median of 4 (relatively stable), which isn't what we get here, but which is what we would get here assuming some reasonable accumulation of partners among the very young in this survey.

Brett Gall writes:

The obvious answer here is to read up on papers using a list experiment to estimate the actual number. I don't have access to these, but they do exist.

Additionally, perhaps the "common wisdom" would be proven correct if we took a conditional approach: the sex-based differences are conditional on the number of partners, occurring only at moderate and/or high numbers of sexual partners because certain types are represented in those populations - i.e. those with one or so partners are unlikely to lie while those with 5+ partners are likely to lie.

In any case, what does item non-response look like for this question, i.e. is there a significant difference between the men and women in non-response? I would be particularly interested in nonparametric estimates of the relationship between non-response and age by sex for this because non-response could be an important omitted variable here. It IS peculiar that the Y-axis scale is so different across sexes.

Hesse Kassel writes:

The most common context to ask about someone's number of partners is when that person is a sexual or romantic partner.

If so that would lead to the most sexually and romantically active people reporting their activity frequently. Those who are not very active would rarely or never report.

That might lead to a general belief in the population that people average more partners than they do in reality. The effect would be huge.

One person with 100 partners would have reported to 100 other people an average of 50 previous partners. Meanwhile 100 people who had only 1 previous partner would report 1 partner, 1 time each. Averaging all the people indicates the average number of partners of close to 2. Averaging all the reports would lead to the impression that the average number of partners is 25.

Floccina writes:

It might be interesting if Hollywood made a movie or 2 about the no partners group (in regard o the subject) and more movies about the 1 partner group.

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