Last year, I wrote a post critiquing some research on 'sexual economics', because they used the supply and demand model as an underlying theory. A better underlying theory is based on a search model (see this post on the economics of sex robots, for example). Usually, we apply the search model to the labour market, but as I note in my ECONS101 class, it can also be used to describe matching in marriage markets, or in the markets for 'shorter-term relationships'.
The simple explanation in the relationship market works like this. Each matching of a couple [*] to each other creates a surplus that is shared between both of them. Because relationship matching creates a surplus, this provides each partner with a small amount of market power (or bargaining power). That is because if one of them rejects the opportunity for the relationship, the other has to start looking for someone else. Each partner is somewhat reluctant to start their search over, so each partner can use that to their advantage. The division of the surplus created by the match will depend on the relative bargaining power each partner. Whichever partner has more bargaining power will get a better deal.
That brings me to this recent article by Kathryn Walter (University of California, Santa Barbara) and 107 (!) other co-authors (spread across 76 institutions!), published in the journal Proceedings of the Royal Society B (open access). Walter et al. reported on a large cross-country sample of over 14,000 survey respondents from 45 countries, and investigated the relationship between sex ratios (the number of males per 100 females) and mate preferences. Specifically:
Participants completed a 5-item questionnaire on ideal mate preferences for a long-term romantic partner. Participants rated their ideal romantic partner on five traits: kindness, intelligence, health, physical attractiveness and good financial prospects. All items were rated on bipolar adjective scales ranging from 1 (very unintelligent; very unkind; very unhealthy; very physically unattractive; very poor financial prospects) to 7 (very intelligent; very kind; very healthy, very physically attractive; very good financial prospects). Using the same scales as for preferences, participants additionally rated themselves on the same five traits: kindness, intelligence, health, physical attractiveness and good financial prospects.
They used these data to construct two measures of preferences for each of the five items: (1) an absolute mate preference (which is the research participant's preference rated from one to seven); and (2) a relative mate preference (which is the research participant's preference, relative to the average of all people in the sample from their city/country, measured as a z-score). The rationale for the relative measure is:
...to account for the fact that the same absolute preferred trait value may be more or less demanding depending on the availability of that trait in the local population.
They also used various alternative measures of the sex ratio, based on the inclusion of different age groups. Using a multi-level model and controlling for various socio-economic differences between countries, Walter et al. find that for relative preferences:
The interaction between sex and sex ratio predicted relative preference for good financial prospects and relative preference for physical attractiveness for every measure of sex ratio...
In general, as men became more numerous, men, compared to women, decreased their relative preferences for good financial prospects, whereas women, compared to men, tended to increase their relative preferences for good financial prospects...
In general... as men became more numerous, men decreased their relative preference for physical attractiveness, whereas women tended to increase their relative preference for physical attractiveness...
The interpretation of these results isn't quite correct, because men weren't becoming more (or less) numerous, because the data were cross-sectional. Instead, we should read it as saying "Ceteris paribus, in cities or countries where men are more numerous..." However, the takeaway message is clear, and consistent with a search model of the relationship market, where bargaining power matters. In places where the sex ratio is skewed more towards men, men have less bargaining power in the relationship market, and women can afford to be choosier, preferring men with better financial prospects and men who are better-looking. The opposite happens for men's preferences - they must be less choosy and can't afford to limit themselves to women with better financial prospects or better-looking women. In contrast, in places where the sex ratio is skewed more towards women, men have more bargaining power in the relationship market, and men can afford to be choosier, preferring women with better financial prospects and women who are better-looking. The opposite happens for women's preferences - they must be less choosy and can't afford to limit themselves to men with better financial prospects or better-looking men.
It is interesting that bargaining power doesn't appear to affect preferences for intelligence, kindness, or health. Walter et al. suggest that this may be because "they are so highly desired, and therefore more invariant". The mean preferences for those attributes were so high, that people are not willing to trade them off at the observed levels of the sex ratio. Perhaps they would if the sex ratio was extremely skewed, but that isn't what Walter et al. observe.
Overall, these results demonstrate that bargaining power matters, not just in the labour market, but also in other situations where matching is a feature.
[HT: The Dangerous Economist]
*****
[*] This same explanation could easily be extended to polyamorous relationships.
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