While we’re critical of much of economic thought on this site, it’s not because economic thinking isn’t useful: it’s because if they’re not assuming that humans are completely rational robots, economists often mistakenly assume that show universals of human nature, rather than particularized, cultural behavior norms. 


As an example, let’s consider one useful economic model, and the ways it can be interpreted: the ‘Marriage Supermarket’. A lot of gender politics can be explained by numbers. Demographic numbers, specifically, which this model is used to ‘prove’. As explained by Tim Harford in his National Bestseller, “The Logic of Life”:


“Imagine twenty single guys and twenty single girls in a room. This is the Marriage Supermarket, so called because shopping is simple, there’s nothing exciting about any of the products, and everything’s under one roof. Getting ‘married’ at the Marriage Supermarket is easy: any man and woman who present themselves at the checkout can collect a hundred dollars (a simple way to represent the psychological or financial gains from getting married) and leave. Naturally, nobody agonizes about whether to get married in the Marriage Supermarket. It’s a no-brainer, because any partner is equally good, and you get cash with no strings attached.”


Harford admits, of course, that this is a tremendous oversimplification of the nature of marriage, but he claims that the model can be used to show something interesting about the issues involved: “That most people would rather be married than remain single and that your gains from getting married depend on the supply of marriage partners.” The first of these conclusions only follows from circular reasoning baked into the model, however, and the second one is problematic because of the unstated assumptions he makes about marriage that go into the model.


Why wouldn’t you get married?


Harford’s first conclusion is definitely true within the model of the Marriage Supermarket. Every (rational) person in a Marriage Supermarket would want to get married. But that follows only from the nature of the model, not from human nature. In the model, the only way to get the benefits of marriage is to get married. Get married, you get some money. If you don’t, you don’t. He’s assuming that marriage provides benefits, then saying that because all rational people would seek available benefits, most people will want to get married. But this just begs the question: does marriage provide benefits? And if it does, is marriage the only way to get them?


I’ll concede the first point, despite the sloppy logic. Marriage provides benefits: friendship and emotional connection, sexual access, economies of scale in communal living with your spouse, the opportunity to create a good environment for child rearing. It also has costs, however. A traditional marriage removes future opportunities to get married or have sex with people other than your spouse. This is a huge opportunity cost. And marriage puts you in a power bubble, where you are vulnerable to abuses of power by your spouse. Maybe your spouse will be a great person, or maybe he’ll take advantage of some power imbalance to dominate your domestic environment. There is no real way to weigh the plusses against the minuses, which are both mostly unknown at the time a marriage is entered into, which is probably why that part of the equation can’t really be modeled.


Additionally, the Marriage Supermarket assumes that there are no other ways to get the benefits of marriage. There’s no accounting for the ability of couples to gain the psychological and physical benefits of marriage before they get married, and yet we all do this. We get a good portion of the benefits of marriage just by dating someone, whether you’re having sex or not, and you avoid some of the negatives - such as the majority of the opportunity cost. 


So yes, in a Marriage Supermarket, everyone will want to get married. But that doesn’t tell us anything about real life.


How much does your marriage give you?


Hartford’s second conclusion is more useful: “your gains from getting married depend on the supply of marriage partners.”


To see how this works, consider the following variation of the scenario, again from Harford:


“Imagine an unusual evening in the Supermarket, when twenty single women show up but only nineteen single men. What happened to the other guy? He’s gay. Or dead. Or in prison. Or moved to Silicon Valley. Or is studying economics. For whatever reason, he is not available… You might think that the slight scarcity of men would cause the women some modest inconvenience, but in fact even this tiny imbalance ends up being very bad news for the women and very good news for the remaining men. Scarcity is power, and more power than you might have thought. 


“Here’s why. One woman is going to go home with neither a spouse nor a check from the cashier. That’s bad news for her. What is less immediately obvious is that the women who do get a spouse are also going to be worse off - and their loss is the men’s gain. Remember that a couple gets to split a hundred dollars when they show up at the checkout; assume that the nineteen couples have provisionally agreed on a fifty-fifty split. 


“The odd woman out, contemplating going home empty-handed, will make the obviously rational decision to muscle in on an existing pairing. The unwanted woman could certainly offer a better deal than a fifty-fifty split, perhaps agreeing to accept only forty dollars. Her rival, being a similarly rational soul, won’t want to lose out entirely, so she’ll counter bid - maybe offering to accept just thirty dollars. The bids will fall until a woman who faces leaving alone is offering to walk through the checkout with some lucky guy and accept just one cent as the price of doing so. He’ll get $99.99; her one-cent profit is better than nothing. 


“The trouble doesn’t end there… No matter what deals are agreed, there will always be one girl left over, offering to pair up for just one cent. The law of one price says one cent is what all of them will get: Anyone on the verge of getting a better offer will be undercut. The nineteen men will each get $99.99. Nineteen women will get a cent each, and the last woman will get nothing at all.”


Now, there are some obvious shortcomings to this model. For one thing, in real life the women probably wouldn’t bid their asks down to a penny: other economic studies show that people have a natural dislike of feeling like they’re getting the raw end of the deal. A woman might accept a 60/40 split of the benefits, but if the offer on the table is just a couple dollars (or less), she’s likely to say, screw it, I don’t need your money, and just walk out of the market on her own. She’s leaving money on the table, which some economists can’t believe would ever happen, but her interest in not being a sucker and being taken advantage of is more important to her than a paltry sum. 


So the results in a real life market wouldn’t be quite so drastic, but the point remains: scarcity of one gender allows the other gender to strike a better deal in relations between the genders. It doesn’t matter whether it’s men or women who are scarce: the other gender will benefit. The real-world consequences of this are significant, because gender imbalances do exist in many situations. Harford notes that single women are more likely than men to relocate to cities in search of wealthy marriage partners, and that the resulting imbalance actually hurts their marriage prospects. Watching any episode of Sex in the City with this in mind is an interesting experience. One might argue that, assuming all of these women are as rational as economists think they are, they’d figure out that the gender imbalance is working against them and move away… but then again, Carrie got her man in the end (and he was rich!), so hope can live on…


Another important example of gender imbalances occurs because young men are much more likely than young women to be incarcerated, especially in poor communities. “In New Mexico, for example,” says Harford (I haven’t done the research to back up his numbers) “30 percent of young black men, ages twenty to thirty-five, are in prison… there are thirty-two states with more than one in ten young black men in prison, and ten states where one in six young black men are behind bars.” These are big numbers in certain communities, and the resulting imbalances make it very hard for women to get benefits from coupling up. This at least partially explains the growing number of children raised by a single mother - women feel compelled to give more to attract a man (which in reality means having sex without much promise of future support) and any attempt to get support from a man is likely to be undercut by an offer of the same benefits from another woman with a lower cost. 


So, for all of the problems with this model, it’s a useful tool in describing certain aspects of gender relations. Harford concludes that in this environment, women are more likely to seek to improve their own economic futures, by delaying having kids and going to college, and that’s a rational response that mitigates some of the effects. But is it that really the best response?


Changing the Model


Going back to the model of the Marriage Supermarket, if we change one little assumption, we can contemplate other solutions to gender imbalances. That assumption, which you might have expected that we would take offense to, is that the benefits of a marriage can only be enjoyed by two people.


Harford believes this because of a rather basic recitation of the Rational Model of sexuality, which is so flawed it’s almost not worth discussing. If you assume that the Rational Model is correct, then you might assume that no other types of relations are possible. But what if it’s not?


Let’s go back to the imbalanced situation, and keep all of the variables the same except for the limitation on the number of people who can get married. Things would start out the same, with all of the women bidding each other down. Then, at some point, all 19 couples would have an agreement to split the benefits 75/25 in favor of the man. According to Hartford’s model, the left-out woman at that point would undercut one of the women by offering to take less- say a $20 share. However, if there’s no two-person restriction on marriage, instead of striking that deal with a man, she can approach one of the women and reason as follows: “Instead of bidding things down even further, let’s agree that the two of us will marry one man. Each of us will take a $25 share, and he can get the remaining $50.”


Now, implausible as it might sound to us, the man in the economist’s supermarket wouldn’t be happy with this plan. After all, he was about to make $75 and anticipating the bidding to go down even further,giving him even more, but now all of a sudden his share is right back to where he started: $50. But he’s not going to be able to find anyone else to trade with unless he offers them more. So he rationally offers a girl $26 and agrees to a $74 share, and the whole bidding scheme reverses. Where does it stop? If you play it out, eventually nineteen couples will have a 51/49 split in favor of the man, but then the left-out woman will rationally offer to take a $48 share, and the bidding will head back down. This is a scenario in which no equilibrium will be reached: if everyone is behaving rationally, the contracts provisionally agreed to will oscillate back and forth between 75/25 and 51/49. In the world of the model, this would mean that nobody would get married. That’s obviously not the case in real life, where eventually people would get tired of the negotiation and accept something in the middle. While the ultimate outcome would still not be good for women, at least they’ve put a cap on their downside: instead of getting bid down to a penny, they’re definitely coming away with at least $25.


But this shows another flaw of the model, and you may have noticed it: in the real world, is it likely that a man would say no to a proposal to marry two women in order to make an offer to marry one (assuming all of the individuals are otherwise equal)? No. We’d call the man incredibly lucky to have ended up with two women to sleep with, and help out economically, and raise children together. The problem with the model this points out is that the “benefits” from the marriage change depending on how many people are married. 


Even if you believe in the Rational Model, that women are after material support and help raising their kids , while men are just interested in sleeping around, the benefits change. If that’s the case, the women in a 3-person marriage where each of them has agreed to a $25 share would still be happy- yes, the man can only give each of them half of his support, but that’s as much as they would be getting from anyone else, since all of the other women have already agreed to take the same share. But for the man? He’s hit an evolutionary jackpot! He gets sexual access to two women, so he gets to double his genetic contribution to the next generation (though he’d probably consciously only be interested in the first half of that reason). So his ‘take’ from the benefits wouldn’t be just $50. However much of that $50 corresponds to getting sexual access to his wife would double: if $10 of the value corresponds to sexual access, he’s now getting $60 worth of value; if it was $25, he’s now getting $75. If his only benefit from marriage is sexual access, then it corresponds to the whole $50 he was originally going to get, and what he’s now on track to get $100 in value. And this higher value that he gets actually stands to improve the value that the women are getting too, because it makes their man less likely to leave them for another woman. 


This could lead to some further negotiation and re-negotiation, based on the value of sex (if he’s really getting $100 in value now, one of the other guys is going to try to undercut him again) but in the interests of simplicity I think we can leave it at that. Allowing marriages to be entered into by more than two people increases the total value that can be created. 


Interestingly, this is the only good argument I’ve heard for biblical polygamy. In situations where there’s a shortage of men (probably caused by war), everyone benefits if the men are allowed to take multiple wives, especially if god has commanded them to ‘be fruitful and multiply’. Of course, this doesn’t justify polygamy in the contexts that we commonly think of it in: mormon polygamy, for example, was (and sadly in some cases still is) dependent on creating an artificial scarcity of men by kicking many of the boys out of the society instead of giving them access to women, and by manipulating young girls so as to make them believe that they could not or should not leave the polygamous society to seek a better deal from the men who have been kicked out. Powerful men in these awful societies bombard the women with propaganda, making them believe that they want to be abused, and force women into marriages before they’re old enough to make their own rational decisions.


But in the absence of those perverting forces, allowing for multiple partners in marriages is good for everyone. This is especially the case when there’s a gender imbalance, but even if there’s not, it can be good for everyone. If you start out with the same number of men and women in the supermarket, but allow for the increases in total value created by marriages of more than just two people, where do you end up?


Let’s assign a couple of values, somewhat arbitrarily. Let’s say that $10 of the man’s gain from marriage is sexual access (this might be an understatement, but it doesn’t really matter). As long as the man’s benefit from paternity certainty is less than that amount (which the Rational Model would deny, but which the Atavistic Model affirms), men would not be opposed to multiple marriages including more than one man. Thus a marriage between two men and two women would create a value of $220 to be divided between the four of them. Women would be okay with this situation as well: because the men are getting bonus dollars from having sexual access to more than one woman, the women can negotiate for a share of the bonus, and everyone ends up with $55. In real life, women gain from having multiple sex partners as well, of course, in terms of personal enjoyment, and (from a cold, evolutionary perspective) it reduces the chances that they won’t be able to reproduce because they have trouble conceiving with their partner. Notice that the more couples join together, the larger the bonus is. A group of 4 women and 4 men would give the men an additional $30 of value from the relationship each (from getting sexual access to 3 more women), creating a total value of $520 to be split among the 8 people, or $65 each.


This is all kind of silly, of course, and assigning these numbers is kind of insulting to everyone involved. The model is absurdly simplified and doesn’t take into account a number of other variables. For example, there are probably diminishing returns from additional sex partners past a certain number, and increasing risk of ‘freeloaders’ the larger a group gets. But what the exercise of running through these numbers suggests is simple: monogamy is bad for everyone economically, and especially bad for members of a gender that is ‘oversupplied’ in a community. The question is, what are we going to do about it?




Supermarket Marriages

by Jackson Lay

September 1, 2014

If only it marriage were simple... but since it's not, let's make up some numbers!

Does the 'oversupply' of women in poor communities end up resulting in more single mothers?

Are two better than one?