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scott cunningham

As for the costs of sex in relationship to AIDS -

It may be the case, too, that in ethnic communities, where biracial matching is relatively rare, and the ratios of men to women are relatively low, that males have disproportionate power in the bargaining over whether or not to wear a condom. It is known, for instance, that women incur more risks from unsafe sex than men, both in terms of possible fertility risks (though abortion and the pill have reduced these), as well as a higher probability of contracting and STD. The probability of infection from male-to-female is 20% higher than it is for female-to-male. Plus, condoms reduce the sensual pleasure for males, and probably have a negligible effect on females. Hence, with asymetries in the risk across the two partners, low sex ratios (and therefore increased male bargaining power in a Nash cooperative game context) and low biracial matching, you may have both increased concurrency (ie, simultaneous sexual partnerships) among men, as well as decreased condom usage. That could account for the HIV/AIDS epidemic among blacks, which exhibit low sex ratios at the urban level (the lowest sex ratio since modern censuses began taking note, actually), low rates of biracial matching, and diminished condom usage.

Also, Emily Oster at Harvard (second year graduate student) has an upcoming QJE publication on HIV/AIDS in Africa and its relationship to the presence of STDs. If there are high occurences of STDs in a population, then those alone may explain as much as 50% of the HIV/AIDS rate, because many STDs amplify the transmission of HIV/AIDS. For instance, ones that create open wounds near the genitalia may amplify the transmission rate of HIV/AIDS.

Lastly, to Paul's point, keep in mind that when you are thinking about disease transmission, you may be dealing with instances where an individual does not fully internalize the social costs of his actions. For instance, we know that STD epidemics are largely driven by both high average number of sexual partners in a population, as well as the variance of the number of parters in that population. If you have a population in which the average individual has several partners in their lifetime, and you have a "core group" of individuals who are extremely sexually active, then that core group can help drive the entire epidemic. Yet, when they increase their partnerships, while putting the network at greater risk because of their high connectivity, they most likely are not internalizing those kinds of social costs (if that is the right way to think about it). Ian Ayres and Katherine Baker have a law review article that came out recently (I think it was either Yale law review of Chicago law review) called "Criminalizing Reckless Sex" in which they discuss one possible policy response to these types of externality problems in sexual networks (they propose to criminalize first-time sexual contacts in which individuals do not wear condoms. It's a compelling article, and discusses the problem not only from an economic perspective, but also from a social norms perspective).


To bring up the conservative community again, Posner says "In communities (and there are still some) in which premarital sex is strongly disapproved, young people marry to have sex, but marriages so motivated are likely to end in divorce, producing more unmarried people and so more demand for nonmarital sex". I don't think this is accurate. We have to ask "Why is premarital sex strongly disapproved?" Probably because of religion. So those that follow the community norm of not having pre-marital sex are probably more religious on average and are not getting married primarily to have sex, but for religious reasons as well (starting a family, etc.). Being raised in such a community, I will say that sex is a strong incentive to getting married - but not the primary factor. I would expect less divorce in such communities because not only are these people more religious and looking for religious people to marry, but just as there is strong disapproval of premarital sex, there is strong disapproval of divorce too. I view this as a good thing. If I have to tough it out through rough times in marriage, I am more likely to have a more fulfilling marriage overall. If I divorce at the first sign of trouble, then I am likely to have multiple, shallow marriages.

Paul Gowder

Also, what's the economic explanation for suicide in cases where there's no terminal disease or chronic disability? Teenagers jumping off cliffs, etc.


Paul, I think you make good points, but the extreme you present is not actually that far off. Economics (or, at least, microeconomics) is the science of decisionmaking under budget constraints. It is not a theory of the world, metaphysics, self-hood, or anything else. It sounds like that is where you are having a problem. Economics merely explains, in positive terms, the process of decisionmaking. Trees maximize the number of other trees they can fertilize under the budget constraints of sunlight, water, etc. If conditions change, they probably will change their fertilization method by the process of genetic evolution. In that respect, physics, biology, and economics are all sciences. Economics is just a specialized form of explaining the process of decisionmaking among humans.

I think humans have some free will, but not unlimited free will. We live in the real world, which is a world of decision-making under budget constraints.

As far as the economics of suicide, Im sure you can guess my answer: that can be explained by extreme conditions in which the value placed on future existence, when perceived benefits and costs are calculated, is negative. It may be unfortunate or tragic or anything else, but that is the explanation for the decision process. The goal for those who want to deter suicide is obviously to try to get the person to value life more and consider costs to be less. Sounds a little dry, but that is part of it. I mean, that is what you usually see in the person on the window sill ready to jump scenes in movies. The hero either tries to encourage a revaluation of some sort.

This sort of explanation tends to be accompanied by criticisms that its life-negating or missing something or whatnot, so as for my own assessment of how it intersects with life, I go to church every week and do lots of volunteer work, but I also enjoy economics. No different to me than being Catholic and accepting Galileo and Darwin.


Didn't Gary Becker win his Nobel partly because of his work in the economics of marriage and such? He's already broken those eggs for a round or two. Judge Posner also has a book on sex and law, though I haven't ever looked at it. Anyway, that's kind of interesting now that they are blogging on the subject.

Paul Gowder

RWS: I guess that's my core objection to economics in general (which shows up in dozens of different ways). It's just so immensely reductive (and yes, life-negating), turning humans to nothing more than the pattern of their choices, and at the same time nihilistic, in that it presumptively makes all decisions (such as the suicide thing) into presumptive cost-benefit analyses -- even when those decisions are influenced by mental illness or drunkenness or some such. (And, indeed, economics probably would impute drunkenness-decisions to some implied cost-benefit analysis in the decision to get drunk...)

I think we need to remember that science (and I'll concede arguendo that economics is a science, though I question the committment of its practicioners to the scientific method) is the servant of philosophy, not the other way around. Human life, being finally constrained by mortality, is only worth anything if it is given some meaning -- any meaning -- beyond that of mere unreflective stimulated action. ("The unexamined life is not worth living," as it were.) There is no question that we in fact have a consciousness that attempts to give meaning to what we do, and that consciousness influences our decisions. In the face of that, I'm inclined to categorically reject any science that refuses to take this consciousness into consideration.

But hey, I'm an existentialist (somewhat). You pick your own philosophical poison. There are any number of schools of philosophy that are perfectly compatible with the reductive theory of economics. However, I think it's important for those who espouse economics to realize that there are also a significant, substantial number of attempts to find meaning for humanity that are incompatible with economics as presently practiced, and are yet still legitimate and both internally and externally consistent. Economics, science though it may not be, is not an exclusive system: its explanations must necessarily permit of alternative, equally valid, explanations.

scott cunningham

Paul, post the entire link. For some reason, that link is not working for me. I keep getting sent to a blogger sign-in page. -sc

The Raving Atheist

This is not because these religions have become increasingly prudish (though Catholicism takes a harder line against abortion than it did until the nineteenth century . . .

Increased opposition to recreational sex may indeed be a sign of increasing "prudism," but I don't see how a change in attitude on the life-and-death issue of abortion can be so characterized.


Hyh's comment: "I'm not referring as much to the incidences of sex in popular media (which is simplay a reflection of the times), but, rather, the use of behavioral science in business and marketing."

I think it's a mistake to see the media as a reflection rather than a projection of the times. Everyone knows that the media is constantly pushing the envelope of what is immoral in order to make it permissible. The media normalizes immoral behavior, an easily observable fact in every medium that I am surprised the judge omits from his analysis.

Paul Deignan

The weakest presumption in this analysis is the idea that the male marries in order to have a stay-at-home wife to raise children. How can this be more than an exception in an economy where the vast majority of couples both work?

So Posner is left with the obvious contradiction to his utilitarian thesis: people marry. On one hand he posits that originally, this was done for sex. Yet, the economies throughout US history were stable in regards to child raising. Couples would marry when they expected to be able to afford a family and raised the size family that could be accommodated by their local economy--all this despite the fact that we did not have social insurance or AFDC. Out of wedlock childbirth was relatively rare. Yet, contraceptives were also rare. So, the human animal must have applied some control that is not being applied today.

Becker seems to believe that such control is impossible. Well, history asserts otherwise.

Again we are left with the question, "Why do people marry?" Posner has no good answer according to his utilitarian view. Companionship does not require marriage.

Well, the answer is obvious (I discussed it earlier). This fundamental dynamic however entirely escapes Posner's model of human behavior. Isn't it odd to have a model of a process with no plausible explanation of the fundamental character of the process?

Geoff Matthews

Pope John Paul II seemed unusually conservative in matters of sex not because he was making Catholic sex doctrine more severe, but because he was refusing to yield to strong pressures to relax it. He was swimming against the tide.
Wouldn't a better metaphor be "He was standing firm against the tide"? After all, he wasn't changing the rules, just reaffirming them.

Ashish Hanwadikar

Didn't Karl Marx try to explain history as a progression of economic (production) relations? This sounds like another attempt to explain the present without any reference to subjective human choice and only as a result of economic circumstances. Not only that it predicts the evolution of the future by extending a "straight line".

scott cunningham

What do you mean Posner has "no good reason for why people marry"? They marry because the the joint utility exceeds the single utilty. Why that is the case mayh be because of public goods within the family (children, for instance), economies of scale, whatever. but there's nothing in Posner's argument that I can detect which states marriage is somehow an anomaly.

Paul Deignan


How is that precisely? Posner does not say. In fact, the criteria underlying the trends that Posner cites do not explain the simple fact that people marry.

The explanation that Posner offers is pathetically weak and contradictory to the great percentage of married working couples in our economy.

How is marriage an economic or social benefit? For a while (before tax reform) it was actually penalized.

It is a gaping hole in his model.

Allen Ayres

"The costs of engaging in sexual activity have fallen dramatically over the last half century (AIDS notwithstanding), for many reasons. One was the discovery that penicillin is a safe, certain, and inexpensive cure for syphilis."

In it's place we have new diseases that have no cure, you're lucky if you just get syphilis - Hepatitis A, B, C, to infinity and beyond!, herpes, venereal warts (HPV), etc... there's plenty we have no cure for, AIDS is just one in a million.

This is not to even mention that penicillin-resistant syphilis, gonorrhoeae, and staphylococci is on the rise...



There's no gaping whole. I don't know what is difficult to understand, but I suspect the source of your confusion is found in your caricature of economics.

Economics allows for social and emotional value. That is included in what economists call "utility." The utility (benefits) of marriage exceeds the costs of marriage for those who marry (or at least expected benefits and costs). Those benefits can exclusively be personal satisfaction. I really don't think you have reflected on this very much. Many monetary exchanges serve purely emotional ends, yet economics explains those transactions perfectly fine. Economics is not just about transactions, but about decision making of any kind. Is that what is giving you trouble? Think of benefits and costs as broadly as possible, and that is what economics uses. Economics isn't just about money and economic growth. It is about human decisiion making. Economists can come to opposite conclusions without ever doubting the power of economic thinking. The difference is found in the assessment of the costs and the benefits. Difference can also be found in how rational individuals behave. Maybe you think humans run more off of instinct without reflection. That's legitimate. But that doesn't mean economics cannot, in its way, explain human behavior. It would only mean that economics provides a false description. Which is your position?

Paul Deignan


Precisely, in economic terms, what is the utility of marriage as opposed to cohabitation?

Saying that economics includes emotional valued items is hand waving.


As far as concrete benefits, there are all those "incidents" of marriage which gays are now clamoring for, apparently. Those nearly one thousand benefits which it is absolutely unjust to keep from them, remember?

Secondly, there is often religious and social value attached to being married over cohabitation. It is a way to signal to your partner and to society a level of committment that cohabitation does not provide. Again, I am not sure what is so difficult to grasp.


It's not hand-waving. One of the things people value which causes them to undergo the marriage commitment is the love and companionship they receive from marriage. Take that benefit out and marriage is less likely to occur. You are correct that it is part of the decision process but wrong to believe that decision science cannot include that in the mix of factors, and also wrong to believe that Judge Posner is oblivious to that. His post is not an all-encompassing statement of his views on these matters or some comprehensive model, and should not be taken as such.

Paul Deignan

RWS, Palooka:

In a model, it is necessary to identify the key forces that make the thing work.

Do people get married for simplified estate planning? Is that what all the trouble is about?

Is there a social stigma to cohabitation that is so serious as to overcome the loss of opportunity (divorces can be costly)?

If for religious reasons, then explain the Catholic phenomena.

Love and companionship? Phooey! That does not require marriage.

Even still, people marry and marry again. Why?

What is the value of marriage?
(If you don't get it by next go round, I will not leave you dangling for long).


Chicks dig weddings.


^ Nail, meet hammer.

Paul Deignan

It is an energy balance.

Marriage provides micro-stability (trading entropy for energy) that allows the couples to concentrate their energies elsewhere.

Sex is an energy sink (not the great recreational source that some imagine--this is actually potential energy being expended that might better be used building castles and such. This is actually a common thread throughout cultures).

That micro-stability is necessary not only to raise children which may have some future economic utility (not so much these days), but also to allow the individuals to focus their productive energies in their professional careers.

Both sides of the equation are seeking security through a social construct that gives up sexual opportunity as the cost of creating the social barrier within which these microcosms of stability can be created.

So, contrary to Posner's take on sex as a good to be acquired and bargained for (this makes no sense when sex is essentially free), it is the stability of limiting sexual opportunity and minimizing its energy cost that people seek in marriage (so much for romance). An integrated society that provides social insurance devalues this security since overall risks to economic viability are lessened. Nonetheless, since the need for economic growth is a consistent force on the individual, we seek ways that allow us to focus our limited energies towards this end. Marriage helps us leverage our energies.

Paul Deignan

Of course it is possible to translate energy to economic values.

The point is that Posner has the relationships fundamentally wrong.

His model would be unstable in terms of marriage.


This essay reminds me of essays that medievals used to write about the origins of the universe and man, etc. Posner uses an accepted modern discipline, economics (in medieval times, exegetical readings of the bible & rhetorical logic) to create a bunch of seemingly plausible propositions, which he strings together into a seemingly comprehensive essay about modern sexual behavior with absolutely no proof. It's more revealing of his own personal prejudices than it is of any "truth." Note especially the paragraph on women entering the workforce--because, he says, of the increased availability of "service" jobs--light labor that we weak women could handle. I have news for Judge Posner--women have always worked, including performing manual labor. Whether we worked outside the home, whether we were paid and whether we controlled our economic products or destiny is another question. Women receive paychecks now, we have a legal right to property, and a theoretical legal right to hold nearly any job we want (excepting, notably, the priesthood). This isn't because now we have a "service" industry which we didn't have before, it's because of changes in the law.

The comments similarly do a better job revealing the writers' (mostly misogynistic) biases. I don't count myself as an exception, don't worry.

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