Sexual economics, a theory in need of reworking

This is a repost of an article I wrote in 2015.  It’s just some good old-fashioned making fun of pseudoscientific nonsense.

Recently, my attention was caught by the idea of the “sexual marketplace”.  Specifically, there’s a theory of sexual economics created by Baumeister and Vohs.  If you’d rather not read the paper, the Austin Institute* made a fancy video about it:

*Apparently, it’s a think tank run by Mark Regnerus.  Yes, that Mark Regnerus.

Note that the video makes a bunch of claims about how people should behave, rather than just how they do behave.  I’ll get to that part later. 

Basic Sexonomics

Baumeister and Vohs (B&V) model sex as an exchange that takes place within a marketplace.  We’re ignoring everything except straight sex because, sure, that’s ~90% of the sex.  So far, fine with me.  Since I’m a physicist I think you can make a simple model of anything.

But B&V add one extra component to the theory.  Men like sex more than women.  Therefore, sex is “sold” by women, and “bought” by men.  Men don’t typically pay in money, but instead may offer

a fancy dinner, or a long series of compliments, or a month of respectful attention, or a lifetime promise to share all his wealth and earnings with her exclusively.

I’ll just grant, for the sake of argument, that men really do want sex more than women, and I won’t discuss whether that’s cultural or biological.  The idea that women are “sellers” doesn’t follow.

In general, sex is an exchange where both parties benefit, regardless of whether anything is bartered for it.  There are people who don’t like sex, but they’re not really participating in the market.  You’d think people would just have sex all the time, but I suppose you need time for other stuff and there’s probably diminishing returns.  I also suppose there’s also some opportunity cost associated with having sex with this person rather than that one.

Anyway, you can imagine supply and demand curves, where the demand curve is the marginal value to men, and the supply curve is the marginal “cost” to women.  Since sex is valuable to both parties, the “cost” is actually negative, but whatever.*  The efficient market price is at the intersection of the supply and demand curves.  Since men want more sex than women, the efficient market price is positive (from men’s perspective).

Image is a graph of supply and demand, obviously whipped up in MS Paint in about 2 seconds. The supply curve is mostly below the zero line, but the intersection between the supply and demand curves is above the zero line.

I worked really hard on this graph so you know it’s right.

However, it is not clear to me that the pricing will be the same across the board.  That may be true in the case of interchangeable products like bread, but is clearly not the case for people.  It may be the case that on the margins, paying women for sex can be the only way to make mutually beneficial agreements, but it’s not obvious that this applies to the market as a whole.  For people who positively value sex, a large range of prices are possible (anywhere between the supply and demand curve shown above).

It is not merely that each person has a different valuation of sex.  It’s that the value of sex is a function of both who you are and who you’re having sex with.  I don’t know how you get from this two-variable function to the supply and demand curves. I don’t know if it’s even sensible to speak of supply and demand curves.  You can’t just assume that all human variation automagically averages out.

B&V also repeatedly emphasize that men are paying by giving the women committed relationships.  So the sexual market, where women sell sex, is coupled to a relationship market, where men sell relationships.  The thing is, like sex, relationships also benefit both parties, and again they ignore that aspect.

This all makes me wonder, where are B&V getting this from?

Although not many others have explicitly discussed sex as a female resource, we believe that that view is implicit, though often unstated, in many writings.  For example, Wilson (2001) recently published a widely influential sociological analysis of the decline of marriage in Western cultures, in the course of which he found it necessary to invoke unsupported assumptions such as […]

Translation: “We may not have much evidence for our theory, but other researchers don’t have evidence for our theory either, so nyah!

In fairness, they offer a bunch of other evidence, such as prostitution, and societal attitudes towards infidelity in men and women.  And certainly, you can fit some facts about our culture into the theory.

However, at times it just seems like B&V are really fishing for the “that totally confirms my pre-existing prejudices” response:

Advanced Sexonomics

Typically, a group of men brought back meat for the group and all the meat was shared.  Miller et al. argued that this arrangement obscured individual hunting ability, and therefore women could not easily use gifts of material resources as a sign of long-term mate potential.

Here’s the obligatory evopsych just-so story.

A low price of sex favors men, whereas a high price favors women.  Therefore, men will tend to support initiatives that lower the price of sex, whereas women will generally try to support a higher price.

And that’s why feminists are in favor of slut-shaming.

Why should a woman care whether men in her community purchase pornographic materials and masturbate? But if pornography satisfies some of the male demand for sex, then it may reduce the total demand for her own sexual favors, and as a result the price she can obtain will be lower.

I guess that is one explanation.

Sexual decision making is likely to be more complex for the woman than the man.  Faced with a suitor desiring sex, she may feel pulled in conflicting directions.

Is there some economic principle that I’m unaware of that says “sellers” are more emotionally conflicted than “buyers”?  (It should be noted that B&V are not economists.)

As social exchange theorists emphasize, the value of any commodity rises and falls with scarcity. […] By analogy, sex would have high value if the woman has had few lovers or is known to be reluctant to grant sexual favors, whereas the same activity might have less value if the woman is reputed to be loose or to have had many lovers.

In my understanding of economics, the value of a commodity rises and falls with global scarcity.  If one person can sell more of a commodity, they simply earn more profits.  So maybe there are some people who prefer sex with sexually inexperienced people, but that’s just an ad hoc preference, not a rational response to the market.

Both men and women said they would be more upset if their partner had sex with a man than a woman.  This fits the view that, in sex, women give and men take.

Again, B&V make it out like this is a rational response to the market, rather than an expression of ad hoc preferences.  I really don’t see how this could be.  Most sex benefits both parties, and it only “costs” women in that there is an opportunity cost.

[cw: rape] A milder version [of this theory] thus holds simply that female coercion of male victims lacks an important dimension, namely theft of the resource, and so the trauma and victimization are less severe.

I really don’t think the theft of resources is the most important factor for trauma!  It’s not like hiring a prostitute and having your check bounce.  Alright, I’m done with this paper!

Normative Sexonomics

Even aside from the merits of sexual economic theory, the video at the top is awful.  It argues that sex has become cheap (because birth control), and therefore men are less likely to pay women with marriage.  The video argues that this is bad.  Therefore, women should collude to make sex more expensive again.

Within their own stupid theory, if there’s more sex and less marriage, this satisfies men’s preferences.  Why is it bad for men to get what they supposedly want?

Message: Men’s desires are destructive to society.

Collusion is kind of a ridiculous idea.  In theory, if enough women collude, this could give them an advantage in a market.  However, the women who are not part of the collusion reap even more benefits, so there’s not much incentive to collude.  The only way collusion is possible here is if it’s coerced.  For example, by public shaming of women who have sex too freely.

Message: We need more slut-shaming.

Saying “sex is cheap” sure makes it sound bad.  However, within the theory, the more expensive sex is, the less equitable the market is, so cheaper sex means more equality.  Note also that as sex becomes cheaper, sexual economic theory becomes less valid.

Message: Men and women have become more equal, and it’s making our theory break down, so we need to stop it!

*Back when I first posted this, some people questioned the negative supply curve, but I still stand by this.  The idea is that if the price were fixed at a negative value (i.e. if women were required to pay men in order to have sex), there would be some women who would willingly pay that price.  I mean, just thinking of it in terms of this wacky economic theory. 


  1. says

    I mean, yes, economists do create models of relationships and sex, but I’ve never seen a serious economist use a perfect-competition commodity supply and demand curve. Most of the real work models trade-offs between search time, breadth, and depth and optimum choice of partner. How long should I look for candidates, how many candidates should I look at, and how thoroughly should I look at each candidate before I make a decision?

    I’ll just grant, for the sake of argument, that men really do want sex more than women, and I won’t discuss whether that’s cultural or biological. The idea that women are “sellers” doesn’t follow.

    I concur with your identification of a nonsequitur fallacy here.

    However, it is not clear to me that the pricing will be the same across the board. That may be true in the case of interchangeable products like bread, but is clearly not the case for people.

    Not clear? You’re being too generous. Even sex with prostitutes is not an undifferentiated commodity.

    In my understanding of economics, the value of a commodity rises and falls with global scarcity.

    It depends on what kind of commodity. If we take the Ricardian view, classical and neoclassical economics are primarily interested in those commodities which we can relatively easily make as much as we want: the trick is to determine how many widgets we actually do want given that we want other stuff too. Scarcity in this view is an immediate-term reaction to a relatively sudden rightward shift in the demand curve. I can explain in more wonky detail if you like.

    Economists generally use the example that we’ll never literally run out of oil; it will just become more expensive to obtain at the margin, so we will use less of it. There’s always enough to supply what we’re willing to pay for it, because the price will rise as we resort to more expensive ways to supply it until it matches the price we’re willing to pay.

    Is there some economic principle that I’m unaware of that says “sellers” are more emotionally conflicted than “buyers”?

    No, there isn’t.

    It should be noted that B&V are not economists.

    No shit, really?

    Normative Sexonomics

    Any mention of normativity should give every honest economist (well, both honest economists) hives. (Never mind that we embed so many normative assumptions in our discipline, we just don’t mention them.)

    some people questioned the negative supply curve

    It’s kind of silly, “paying to supply” is just demand, but it’s less silly than a lot of models actual economists use.

  2. says

    Is there some economic principle that I’m unaware of that says “sellers” are more emotionally conflicted than “buyers”?

    Well, actually kinda, maybe. Some Behavioral Economics experiments have shown that people value an object that they own or possess more than they value an identical object they do not possess. I’m not sure if that counts as “more emotionally conflicted”, though.

  3. siggysrobotboyfriend says

    You say that the cost of sex for a woman is mostly opportunity cost, but I think you’re missing the important fact that sex is in general more costly for women than men due to the risk of pregnancy. The main benefit of pregnancy (passing on your genes) is the same for both parties, but the costs of pregnancy are not remotely evenly distributed. Typically, only the woman incurs the costs of going through pregnancy and giving birth, and she’s also expected to do most of the work of caring for the child after it’s born. The man will also incur costs (financial responsibilities, limited caretaking responsibilities) but they’re not nearly as high as what the woman pays in exchange for the same genetic benefit.

    Reliable contraception mostly addresses this, but people often lack reliable access and and contraception that has to be used repeatedly has a serious trembling hand problem. People rarely use condoms every time and people on birth control pills miss doses.

    I’m not sure how this affects the bottom line conclusion but we should consider it when evaluating the costs and benefits.

  4. VolcanoMan says

    This paper (and accompanying video) is crap. For a few reasons. I think the most important one is that male and female enjoyment of sex are both going to fall on a normal distribution. The MEAN of male enjoyment of sex may well be higher than that for women, although if this is the case, I would like to see someone prove to me that this isn’t merely a result of cultural expectations. Also, the variance could be significantly different between men and women – perhaps the women who enjoy sex the most actually enjoy it a lot more than even the most promiscuous men, but maybe you see more asexual women than men, creating a wider distribution of preference. Therefore, as noted above, there really is no fixed price for sex. If you have a woman who likes sex more than her male partner, is HE the one who’s selling the relationship back to her, in the quid pro quo exchange hypothesized about in the paper? This whole thing strikes me as one big “just so” story (well, it IS evo-psych after all!) that makes an embarrassing number of assumptions in (surprise surprise) confirming the biases of its authors. Men are pigs because they just like sex that much more and are unable to control their urges…women are prudes because they dislike sex and they’re manipulative sluts because they use sex to lure unsuspecting men into relationships. If women colluded with each other to reduce the supply (which wouldn’t be hard according to these authors, since they hate sex so much) they could raise the value of sex and then men would be forced to take part in a marketplace in which they had to be on their best behavior, or they wouldn’t get any. Rape culture solved! Ugh.

    This is all kind of unfortunate, because I suspect there IS a behavioral economics story to be told here, a story about mate selection. If you have an obvious trait that is shared by the vast majority of people in your country, you have no way of easily standing out (especially since most people make snap judgements about people that are hard to change), and your chances at finding a mate depend on your ability to sell yourself, to emphasize what makes you different. If that obvious trait is rare, and of perceived high value in another country though, you will be in higher demand there, and so the ability to enter and sustain a relationship there will be greater than in your own country. You will have to do less work for a similar result. For example, white foreigners in China are fairly rare, and due to a relic of an agricultural society, light-colored skin is of perceived high value in Asian countries – in the recent past, only the most elite individuals had lighter-colored skin, signalling that they didn’t have to work in the fields and get all tanned. So a white person who may be considered basically average at home in the US or Canada would have little trouble attracting romantic interest from people in China. This is only one, fairly simplistic example, and it doesn’t take into account nuances of personality and compatibility, but traits of personality would also vary in value depending on where you are. Continuing with the America vs. China paradigm, America is a very individualistic society while China is largely collectivist. So not only would white skin set you apart, but your individualistic perspective would be new and different, and likely to set you apart automatically. People select their mates for all sorts of reasons, rational and irrational, conscious and subconscious. So economics shouldn’t be tossed out the window when dealing with sex and relationships – it’s just that the authors of this paper are out more to prove an ideological point than to do good science.

  5. dangerousbeans says

    This makes me glad I’m gay and non-monogamous

    There is also the cost of getting killed by your boyfriend

  6. says

    Have the people who thought up this theory ever actually met a woman and talked to one?
    I mean, since the infamous “I noticed you around, I find you very attractive, would you go to bed with me” story it seems like male researchers have asked a couple of superficial questions and then run wild with the results.

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