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What about the natural gender ratio that neatly supports monogamy, as a corollary to polygamy condemning some men to celibacy?

Determinant, ah, yes, the gender ratios question. There is some evidence that marriage patterns actually impact gender ratios. So, for example, the selective abortion of females found in predominantly-monogamous China does not occur in the more polygamous parts of sub-Saharan Africa. And communities such as Bountiful, British Columbia, that practice polygamy actually force many boys out of the community once they reach adolescence. At the same time, when there is a high population growth rate, polygamy can be accommodated by having men married at a relatively older age and women marry relatively young, as there is more than one 14 year old girl for every (say) 28 year old man. So, yes, I did simplify somewhat in the post.

Imagine if one of Tiger's flings has resulted in a child... Mom and offspring would be set for life.

I suspect that women will, on average, tend to try to do whatever is best for their (potential) offspring. If it's better to be the King's bastard than the legitimate heir of serf, I suspect the King will be getting plenty of tail (to put it crudely).

GBS: "Polygamy when tried under modern democratic conditions as by the Mormons, is wrecked by the revolt of the mass of inferior men who are condemned to celibacy by it."

This seems not to have happened with the Mormons. Aside from the pockets where polygamy is quite open, it is still not uncommon among Mormons in Utah, where secondary wives are on welfare and are not legally or officially married by the Church. (I do not know about Mormons in Canada.)


Also, to discuss the economic aspects of polygamy, do we not need to include polyandry, which is or was practiced where living conditions are harsh?

Polygamy was suppressed in the the Mainline LDS Church as a condition of Utah being admitted as a State in 1896.

@Patrick - precisely.

@Min - yes, strictly speaking I should have said "polygyny" which means one man/more than one wife, as opposed to the more general term polygamy. As you rightly point out, the economics of polyandry, which typically involve related males e.g. brothers sharing a wife, are quite different. Perhaps I was oversimplifying in an attempt to keep things simple.

@Min - on Mormons - as I noted earlier, contemporary Mormon communities where polygyny is widely practiced maintain an unbalanced sex ratio by excommunicating young men.

And another caveat (before Linda writes an appalled comment): another massive demographic change that I've totally ignored is the empowerment of women. One reason that some groups e.g. the community in Bountiful BC are able to sustain polygyny is that women have limited power to leave: to leave means taking a risk that you will never see your sisters or mother or other family members again, that you will be unable to practice your faith,that you will lose custody of your children. Plus assets are held in such a way that receiving child support or alimony or even any division of the marital assets is impossible.

Which I've ignored.

Because I still think the possible (if completely untestable) connection between rising income inequality and greater acceptance of polygamy is interesting.

You know, I've wondered about the question (a variation on Greg Mankiw's Height Tax) of why we think it's okay to forcefully redistribute income to increase equality, but not forcefully redistribute sex to increase equality in that - for instance, by requiring all men and women to have sex with one person per year who would otherwise (due to inability to find a willing partner) be celibate. After all, sex is a basic human need/instinct, and generally our income redistribution measures are above the pure survival level anyway.

Maybe a form of such a redistributive measure already exists through the ban on polygamy.


If we legalize prostitution, redistributing money *is* redistributing sex.

Well, I will try not to sound too appalled. I do wonder, though, if you are not using too broad a paintbrush. You seem to be conflating several different types of arrangements: formal marriage, marriage with recognized mistress - are all those French stereotypes true? What's happening with wealth inequality in France? - one-night stands, serial marriage...Surely they are all related, but can we link them to different levels of income inequality without considering length of life, job markets, inheritance rules, child support, social norms regarding extra-marital sex (which must be related to income distribution across the sexes, if not directly to income inequality....).

"Surely they are all related, but can we link them to different levels of income inequality without considering length of life, job markets, inheritance rules, child support, social norms regarding extra-marital sex (which must be related to income distribution across the sexes, if not directly to income inequality....)."

@Linda, my sense is that the literature on income inequality and polygamy has largely ignored these types of complexities, especially income distribution across sexes. The one subtlety that does get discussed is production technology - e.g. with certain types of technology (unskilled production) quantity of children may be more important, with others quality may matter more, and when quality of children matters more polygyny is less attractive.

Empirically it's hard to find the data, and complex social interactions are hard to model theoretically.

It's just that polygamy seems to be out there more than it used to be. I honestly did not see this editorial in yesterday's NY Times before writing this post:


"What we think of as “traditional marriage” is not universal. The default family arrangement in many cultures, modern as well as ancient, has been polygamy, not monogamy." -

Well, it wasn't just Linda wondering about that point - the decline in male-female labour market inequality would have struck me as a reason why we wouldn't see inequality translating into as many mistresses as in the past (assuming that it did back somewhen). Even if just because it has been associated with a decline in available time on the part of potential mistresses? (Could write up a vaguely interesting model, throwing in time rather than money search costs, perhaps.)

@Christine and Linda, it's easy enough to write down a model where an increase in income-when-single increases women's "reservation wage" and therefore decreases the number who are willing to become "second wives." I haven't written down a formal model, just exam questions that you could easily enough generalize, like the one below (though my students point out that I'm assuming in a very sexist way that men could demand more than one wife but women can't demand more than one husband). But if Ted Bergstrom can't get his paper on polygyny (the first link at the start of this post) published...?

Polygamy on Freelove Island. There are 10 men and 11 women on Freelove
Island. All men on Freelove are equal. They are prepared to pay their first wife a marital wage of $2,000 per month and their second wife a marital wage of $1,000 per month. Women can earn $1500 a month if single.
a. Draw the supply and demand in this marriage market, and calculate the
marital wage in equilibrium. How many marriages will there be? Ignore
love – assume that people will get married as long as their marital
wage is higher than what they could earn if single. (10 marks)
b. On Freelove, polygamy is legal. Will there be any polygamous marriages?
Why or why not? (5 marks)
c. One Freelove Island resident, Jon, wins Lotto 6-49. Now the marital wage
he is prepared to pay is (10-n)*1000 per month where n is the number of
wives Jon has. Draw the new demand and supply in the marriage market.
What is the equilibrium marital wage? Will there be any polygamous
marriages? Why or why not? (10 marks)
d. Take the situation in part (c). Now, if the men on Freelove had a vote,
would the majority vote to allow polygamy, or to ban polygamy? Explain
(5 marks).
e. Drawing on your answer to (a) through (d) above, as well as the readings,
discuss what kind of societies you would expect to be polygamous, and
what kind of societies you would expect to be monogamous. (10 marks)

Frances, this thread is in danger of descending into Mormon-bashing. The communities which practice polygamy i.e. Bountiful are not part of the regular LDS church based in Salt Lake City. They are fringe groups.

I'm not an LDS member nor do I agree with anything they say, but this thread is trafficking in stereotypes more than getting at real economics.

Plus monogamy as a species strategy ensures that that as many people as possible get a mate and thereby ensure genetic diversity. Plus it minimizes the reproductive risks wrt an individual.

That's why it's the norm, not polygamy.

One factor I believe that needs to be considered is the legalization of gay marriage and the growing social acceptance of gay relationships. Since a significant portion of the population is bisexual (~3%) it can act as an equalizing factor.

Determinant, from a species survival strategy, it makes sense to pass on only the best genes - so if your species is one where men contribute genetic material and not much else (so not penguins, for example), it makes sense from a biological point of view to go for the best.

Take a look at the first link in the post - there's some stats on the number of societies that practice polygyny - it's very common geographically and historically. Then lack of rights for women, wealth inequality and lack of investment in human capital have been very common geographically and historically also.

I've edited my comments above to reflect your concerns about stereotypes.

I agree it's impossible to do a definitive empirical test of whether there's a link between the rich getting richer and extra-marital affairs. But here's a suggestion:

Perhaps you could use Google Trends data — essentially it's data on how often people search for a specific term. One might suspect that searches for "affair" are a good proxy for how often people actually have extra-marital affairs (Hal Varian has written a paper about how well the search data may or may not explain real-life phenomena: http://google.com/googleblogs/pdfs/google_predicting_the_present.pdf). There is data across years and across countries, so while it's not at the individual level but you could examine whether there's a correlation between affairs and average or median income of the top X% of the population (or whatever similar economic stat you can track down for a large number of countries).

As for the possible relation between the rich getting richer and extra-marital affairs (or polygyny) it seems to me that it can cut both ways. If you start from equality you can see lower status men getting left out, with women gravitating (levitating?) towards upper status men. OTOH, if you start from inequality and get even less equal, you may have fewer high status men, for whom the next wife is more trouble than she is worth. Then you may have men who lose status also losing wives, for an overall reduction in polygyny. No?


One of my profs thought that, back when it was common for families to take in single men as boarders, many such arrangements became polyandrous. Perhaps increasing inequality may lead to more polyandry. ;)

"If it's better to be the King's bastard than the legitimate heir of serf, I suspect the King will be getting plenty of tail (to put it crudely). "

And when becoming King was more a matter of how many other would be King's heads you managed to cut off rather than whether you were the son of the previous King this was a definite incentive to start cutting off heads.

Translate into the modern day and I'm sure we could find a link between income (or wealth), the incentives to gain it and the associated status and the desire to be getting more tail.

Tim - there's been a paper or so (and sorry, I'm too lazy to find the reference for you) that links China's high savings rate to the high male/female ratio: men save because they hope to find a partner. So I think there's truth in what you say.

Min - prostitution is the classic polyandrous relationship, though yes, boarding houses did (do) sell women's domestic work. My impression is that domestic work is totally ignored in this economics of polygamy literature, which is unfortunate, because the difference between various types of relationships, e.g. two wives in the same household, two households, one night stands etc often turns on the amount of domestic work expected.

There's actually been a number of papers written recently on the economics of prostitution. I don't really have a sense of the factors influencing the demand for prostitutes - the supply is straightforward enough, women do it because it's better than the alternatives.

David, interesting idea. "affairs" doesn't work as a search term because it's such a common word, as in "international affairs." "Extramarital affair" tends to spike with particular news stories, as in "Governor admits extramarital affair." Polygamy is trending downwards over time (so much for my theory) but Ashley Madison is trending upwards.

Mike, for an estimate of the size of the gay, lesbian and bisexual population in Canada, you can see my paper,
People need love and affection, and adapt to circumstances - there's an amazing account of the history of Australia - The Fatal Shore - that talks about the extreme sex ratio imbalance during the convict period and the resulting phenomenon of men having sex with men (oddly enough, this was one of the reasons Australia stopped being used as a penal colony - the 'immoral way of life') people were living.

Thing is - late 1800s Utah didn't have much of a problem with men being left without wives.

It's a matter of simple population demographics, and historical details about the practice of polygamy in 1800s Utah.

First off, the vast majority of Mormon men in Utah only had one wife. Polygamy was not required, and most men didn't have the financial means to pull it off. So they didn't bother with it.

Secondly, the men tended to marry, on average, women about 2 to 3 years younger than they were (just like everywhere else in the US - child brides were no more common in Utah than they were anywhere else in 1800s America).

Thirdly, the population was steadily increasing. This meant that each succeeding generation had more people in it than the previous one. This meant that for a given 25 year old Mormon man, there were always about 2 or 3 eligible 21 or 22 year old females available. On average anyway. Overlay the two population pyramids, and you'll see what I mean.

Actually, the word "pyramid" works pretty well, because that's essentially what Utah polygamy was in the late 1800s - a marital pyramid scheme. As long as the population continued to grow, Utah polygamy would have been sustainable indefinitely (in theory anyway, and not adjusting for other variables).

So the phenomenon of "lost boys" or "disenfranchised single males" was no more a problem in late 1800s Utah than it was anywhere else.

The modern FLDS Church faces entirely different population demographics - and thus suffers from these problems.

To be more specific, even in societies where it is allowed, polygamy tends to be rare on a large scale. Saudi Arabia allows men to have up to four wives, but for every Ibn Saud (the first King of Saudi Arabia in 1932, had approximately 22 wives by serially marrying and divorcing so that he was only legally married to four at a time) there are thousands who have only one wife.

The economics of supporting multiple spouses and their children puts an upward brake on polygamy in most societies.

Frances, good point about the word "affair." Interestingly, it appears "polygamy," "cheating" and "mistress" all have similar-looking downward trends, but "Ashley Madison," "affair" and "extramarital affair" look quite different. It does raise questions about the robustness of the Google Trends data in terms of how well it'd serve as a proxy for the prevalence of extramarital affairs. Although "Ashley Madison" may not be a good measure because it's just one website which may have an upward trend because of advertising, "affair" may be bad for the reason you've mentioned, and it appears "extramarital affair" may be wonky because it's not searched very often.

Evolution is not about benefit to the "species". If it were, the sex-ratio would everywhere be completely lopsided toward females (one male can fertilize many females, additional ones are surplus). Why does the sex-ratio tend to be 50-50? Because the smaller the ratio of one gender, the greater the expected fertility of a random member of that gender (the total fertilities of both genders must be equal, smaller denominator means higher average).

There is a story about actor David Tomlinson who is best know for playing the father in Mary Poppins. He was on the train on his way out of London to his parents luxurious home located in the stock broker belt, when he glimpsed his father through the window of a small row house. Thus he discovered that his father had two "wives" and two families. I can't confirm this story by a Google search but it illustrates a point. The information age means that these situations get discovered and made public. In those days there was no finding pictures on Facebook. It is true that we are moving toward more income inequality, but the time of relative equality was a blip in human history. I would say that the biggest change has been our inability (and also unwillingness) to have secret relationships.

Don't you have something better to do than speculumtate like this? It seems that your mind, thus engaged, hit an endless repeat cause the music played on for me:
Liz Taylor, Zsa Zsa Gabor...

Inequality or Celebrity - that is the question.
Whether it's easier to play the long game with one forever,
Or to divorce at the first sign of trouble and by unproposing, end it.

In a way our steadily expanding sex trade can be considered an example of increasing effective polyandry, corresponding to our increasing effective polygyny remarked in the post.

What's interesting is that socially, our sort of polygyny is associated with high social status, while our sort of polyandry is associated with low social status (both for provider and for most of the consumers).

In the extreme case, one could argue that a society with high enough social inequality would feature the regular institution of enforced polyandry by slave prostitutes to provide sexual services to low-class male consumers, while harems are maintained by men at the top end of the spectrum.

That profile would seem to at least roughly match most empires of olden time.

Ah, the joys and pleasures of sharply unequal societies!

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