It's clickbait, New York Times style: "Does a More Equal Marriage Mean Less Sex?" Spurred by findings of a paper by Sabrino Kornrich, Julie Brines and Katarina Leupp published in the American Sociological Review, the article argues that, "too much similarity in egalitarian marriages leads to boredom and decreased sexual frequency". In general, "the less gender differentiation, the less sexual desire.” "On an emotional level, “kindred spirits” sounds lovely. But when it comes to sexual desire, biology seems to prefer difference."
But do these findings really stand up to serious scrutiny?
The key findings from the Kornrich, Brines and Leupp paper are summarized in the picture on the left. Sexual frequency (measured in times per month) is increasing in the men's share of non-core housework (things like car repairs), and decreasing in the share of core housework (things like vacuuming and laundry). The average proportion of core household chores done by men was, according to men's reports, 0.25. With that sharing of housework, a couple is predicted to have sex about once a week, or just over four times per month.
The graph looks impressive, but just how big are the reported effects? The standard deviation of men's share core housework share was 0.19, and the estimated coefficient on that share was -0.416. Because the authors used a negative binomial regression, and sexual frequency isn't normally distributed it's not entirely straightforward to know how big these effects are. But roughly speaking, going from say the bottom quarter of the household chores distribution to the top quarter would change sexual frequency less than once per month [corrected].
This is what we're getting so hot and bothered out about? Really?
Sharing of household chores might explain some of the differences in sexual frequency across couples, but the effects are not, by any stretch of the imagination, large ones. I don't have access to Kornrich, Brines and Leupp's data, so I can't replicate their findings. But I do have access to the Canadian Community Health Survey, which has a certain amount of information on the frequency of sexual activity.
I don't know if it's safe to conclude from this graph that the sexless marriage is a myth - after all we don't know who married people are having sex with. It may not be with each other. Plus people may not always give honest responses. But almost all married people under the age of 50 have sex at least sometimes, while about 30 percent of divorced/separated/widowed people in their 40s have not had sex in the past year.
While not entirely conclusive, this graph makes me strongly suspect that the kind of differences in sexual frequency reported by Kornrich et al are dwarved by the differences in frequency of sexual activity between married individuals and single or separated/divorced/widowed individuals.
The between sample variation completely swamps the within sample variation.
The basic logical flaw in the New York Times article should now be clear. The NY Times is arguing that, conditional upon being married, sharing of housework results in less frequent sexual activity. Yet it seems not at all unreasonable to suppose that willingness to share housework might have some impact on the probability of couples staying married. If sharing housework makes it more likely that a couple will stay together, then it's entirely possible that those with more egalitarian values get more nookie, not less.
Put another way: for a marriage to stay together, someone has to be getting something out of it; if not sex, then sharing, or friendship, or companionship. Kornrich et al may be right that men with traditional attitudes towards marriage have more sex - if they can persuade someone to marry them, and stay married to them. Otherwise - well, once you're over 40, the outlook isn't good.
Note: graph created by the following stata code:
recode sex 2=0
graph bar (mean) sex [pweight = WTS_M] if DHHGAGE<=9 &DHHGAGE>=5, over(DHHGAGE) over(DHHGMS)
and then doing a bunch of fiddling about to make things look pretty.