10 Interesting Facts on Relationships & Sex
Q1 2025
Every few months, I summarize the evidence I’ve gathered that relates to the article series The Game Theory of Relationships and Sex (articles 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13 so far). Today, the latest includes:
Why wearing heels make women attractive
One solution to the fertility crisis
How making more money has impacted women’s marriage rates
How much do women still care about men’s income?
Who is happier in marriages
Why do marriages end?
The ideological divide between men and women
Why are women sexualizing more?
Why are most men ugly?
Are married men more attractive?
1. Sexiness: Lumbar Curvature
Yet another physical aspect that is attractive in women: lumbar curvature!
Which one seems more attractive to you?
If you said b, congrats! That’s indeed found to be more attractive!
Apparently that’s one of the reasons why women wear heels: Raising the ass compared to the rest of the body forces the lower back forwards, which then forces the upper back to arch backwards to keep the body standing.
Apparently there’s an optimal angle: 45º!
The relationship between women's lumbar curvature and physical attractiveness.
And why is this more attractive?
Because apparently women with this lumbar angle have fewer pregnancy problems! Once again, we’re seeing the connection between attractiveness and fertility. It’s everywhere!1
2. Solutions to the Fertility Crisis
WFH boosts fertility dramatically.
3. How Have Marriage Prospects Evolved with Female Income?
In general, fewer women marry, so we should not be surprised to see that women of most income brackets are less likely to marry today than 50 years ago.
It’s interesting to see however that relative to that baseline, the more the woman earns today, the more likely she is to be married!
How can we interpret this? I think it means that it was much rarer for women to work jobs that made a lot of money in the past, and probably not as well regarded. This is now more normalized than it used to be, so high achieving women are more likely to marry than they were before. Society is progressing!
4. But Relative Income Still Matters
Husbands with much higher incomes than their wives are less likely to divorce.
Couples married between 1990 and 2018 had an 8.4% chance of divorce by 2021 when the woman made more than the man. The more money the man made vs the woman, the more that rate dropped. When husbands made between 0 and $38k more per year, the chance of divorce was 4.8%. When they made more than $38k more, that rate dropped further, to 2.9%!
This trend is also true in egalitarian Sweden.
In that same country, big wealth windfalls favor marriage for men but not for women: When men won the lottery, they tended to have more children, married more, and divorced less. When women won the lottery, they tended to divorce more.
In other words: When the man makes more money, women stay more. Is it because women enjoy marriage less, or is it something more genetic?
5. Women Initiate More Divorces
According to this 2015 study, 70% of divorces are initiated by women.
Interestingly, that rate went down to 50-50 when researchers looked at non-marriages: Standard breakups were much more evenly split.
Unsurprisingly, more than once I’ve heard comments like: We live in a patriarchal society, where men do way less than they should in marriage! That’s why women divorce more. It’s a bad deal for them. This has to stop! Men must contribute more!
If this were true, you’d imagine that gay men divorce at a much higher rate than gay women: Surely, if men are bad at relationships, two men in one relationship will be unbearable! In fact, the opposite is true. Lesbians are over 2x more likely to divorce than gay men! The same is true across countries.2 It looks like the more women there are in a relationship, the more that couple is likely to break. This suggests the cause of relationship breakdown is more due to women than men.
I asked ChatGPT why it thought this could be. Here are its hypotheses:
Sexual intimacy: Men are more interested in sex and have more of it, and that stabilizes the relationship.
Women want commitment very quickly, so they might be more likely to marry quickly—including the wrong person.
Women have higher expectations of emotional intimacy—expectations that are frequently unrealistic.
Women get more emotionally vested in conflicts, and this makes conflict resolution harder.
Men make more money than women, and money brings stability.
I asked a group of friends what their hypotheses were, and these are the suggestions from women that make sense to me:
Women are more dissatisfied in general.
Women like independence more than men.
What’s clear though is that “the patriarchy and the resulting poor behavior of men in relationships” is unlikely to be the root cause of most divorces. Ponder this next time you hear this complaint.
6. Who Is Happier in Marriages, Men or Women?
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