More Sex is Safer Sex

In More Sex is Safer Sex Steven Landsburg famously argued (based on work by Michael Kremer) that if more people, especially more sexually conservative people, had sex the AIDS epidemic could be reduced.  Landsburg wrote:

Imagine a country where almost all women are monogamous, while all men
demand two female partners per year. Under those circumstances, a few
prostitutes end up servicing all the men. Before long, the prostitutes
are infected; they pass the disease on to the men; the men bring it
home to their monogamous wives. But if each of those monogamous wives
were willing to take on one extramarital partner, the market for
prostitution would die out, and the virus, unable to spread fast enough
to maintain itself, might well die out along with it.

In The Wisdom of Whores (see also my earlier post) Elizabeth Pisani says that such a country exists, it’s Thailand, and the results of more sex was safer sex – exactly as Landsburg argued. Here’s Pisani’s story:

Thailand used to fit the the classic ‘virtuous girls, philandering boys’ model.  At the start of the 1990s, 57 percent of twenty-one-year-old men in Northern Thailand trooped off to the brothel to do their philandering.  More than half the sex workers who soaked up their excess energy were HIV-infected….

Then…the Thai economy boomed.  Girls were getting better educations than ever before…Educated girls were waiting longer before getting married, but not before having sex.  By the end of the 1990s, 45 percent of girls aged 15-21 in northern Thailand admitted to having sex with boyfriends before marriage, compared to less than a tenth of that in a nationwide survey in 1993.

…So at the end of the decade, we have a lot more premarital sex and not all that much condom use with girlfriends.  But now that these young, cash-strapped guys can have sex without paying, they’ve stopped handing over cash for sex.  By the end of the 1990s, only 7 percent of young men were paying for sex, and HIV prevalence in sex workers had come down too.

….In short, more women having premarital sex equals less HIV.

Pisani cites neither Landsburg nor Kremer so I believe her account is independent.  Note that Pisani also credits Thailand’s successful condom program.


'size matters,' then 'more sex is safer sex.'

Well, how does this square with the belated admission that the AIDS "epidemic" was not assocciated with heterosexual sex?

"Imagine a country where almost all women are monogamous, while all men demand two female partners per year. [...] But if each of those monogamous wives were willing to take on one extramarital partner [...]"

You could just as easily rewrite that to say: "if each of those promiscuous husbands were willing to take on one fewer extramarital partner" and prove that less sex is safer sex.

The assumption is that one group absolutely will not change its behavior, therefore the other group has an obligation to do so. But who gets to dictate which group is which?

More sex is probably good, but concurrent relationships are very, very bad.

I think I recall from earlier inquiry following a post here (several years ago) that having concurrent relationships was a major factor in the rate of spead for HIV. The number of parners a person has doesn't seem to have a big impact, it's having more than one at a time that really increase tranmission. I believe there was a study and one of the big contributing factors is that the viral load in the human body is highest during the first few days of contracting the virus, so transmission rates are higher.

I'll see if I can dig up the sources.

Alex's post which addresses concurrent relationships. Of course, the analysis was based on models.

Here's another article.

Stage of Disease
There is now compelling evidence that for HIV-infected
individuals, infectivity is not constant over time but varies by
stage of infection and viral load.2,5 Most studies agree that the
probability of transmission peaks at the early (acute) stage of
infection, decreases during the latent stage, and then increases
again during the symptomatic stage.
At the population level, however, there are 2 reasons that
might explain why individuals in the primary stage of infection
contribute the highest proportion of secondary infections:
heightened infectiousness during acute infection or a period of
higher contact rates that leads to infection and secondary
transmission in short succession. Biology and behavior can be
confounded here, and they may both contribute.
Jacquez et al6 were the first to use mathematical models
to emphasize the importance of primary stage transmission.
Using a computational-deterministic model, they showed that
an interval of high contagiousness during primary infection
followed by a large decline in infectiousness was consistent
with the pattern of epidemic spread seen in cohorts of men
who have sex with men (MSM) in the early years of the
epidemic. These findings depend on many assumptions: that
people have serially monogamous relationships, that there is
random mixing by activity levels, on population prevalence,
and on the distribution of persons in each stage of infection.
Changes in any of these assumptions would change the findings.
A recent modeling study reanalyzed these data and
pointed out that the time spent in each stage (the duration
component) is an equally important factor in determining the
impact of infection stage on transmission. Given the much
longer time spent in stages after primary infection, it is argued
that the impact of primary stage infection on overall incidence
declines dramatically as an epidemic matures.7 Thus, an
individual-level effect (higher primary stage infection) may
not drive the population-level outcome (incidence).

I'm not really familiar with the work, but the model does at first glance appear to be overly simplistic. And how can we determine whether the change in Thailand was due to sex habits or condom usage? Seems to me this still falls into the category of interesting ideas that may or may not be true.

In Africa, long term concurrent relationships (rather than serial monogamy seen in the U.S. and many other places) are often blamed for high rates of HIV transmission among heterosexuals. People are most contagious right after they get the virus, or if they have a sexually transmitted disease. Some might argue that an occasional visit to a sex worker, who may have been infected with HIV for longer, and with whom you are more likely to use a condom, is less risky than interlocking heterosexual networks of concurrent partners who don't use protection. In short, it depends a lot on messy human behavior.

A previous poster says a "new equilibrium" will be established soon after an influx of previously abstainers, and then jumps to the conclusion that with more sexually active people, the new equilibrium will entail more infections. As the Landsburg hypothetical shows, however, the new equilibrium could well be one with less infection, or even one where the disease dies out completely.

Landsburg's theory has been tried on a vast scale -- across much of Africa -- with a cataclysmic results. AIDS is so bad in sub-Saharan Africa in part because it has a different sexual structure than much of the rest of the world. One of Africa's big AIDS causes is not Castro Street-style promiscuity, but multiple concurrent partners, exactly like Landsburg's model:

From a 2007 article in the Washington Post:

Speeding HIV's Deadly Spread
Multiple, Concurrent Partners Drive Disease in Southern Africa
By Craig Timberg

FRANCISTOWN, Botswana -- †¦ A growing number of studies single out such behavior -- in which men and women maintain two or more ongoing relationships -- as the most powerful force propelling a killer disease through a vulnerable continent.

This new understanding of how the AIDS virus attacks individuals and their societies helps explain why the disease has devastated southern Africa while sparing other places. It also suggests how the region's AIDS programs, which have struggled to prevent new infections even as treatment for the disease has become more widely available, might save far more lives: by discouraging sexual networks.

"The problem of multiple partners who do not practice safe sex is obviously the biggest driver of HIV in the world," said Ndwapi Ndwapi, a top government AIDS official in Botswana, speaking in Gaborone, the capital. "What I need to know from the scientific community is, what do you do? . . . How do you change that for a society that happens to have higher rates of multiple sexual partners?" †¦

But the number of sexual partners is not the only factor that increases the risk of AIDS. The most potentially dangerous relationships, researchers say, involve men and women who maintain more than one regular partner for months or years. In these relationships, more intimate, trusting and long-lasting than casual sex, most couples eventually stop using condoms, studies show, allowing easy infiltration by HIV.

Researchers increasingly agree that curbing such behavior is key to slowing the spread of AIDS in Africa. In a July report, southern African AIDS experts and officials listed "reducing multiple and concurrent partnerships" as their first priority for preventing the spread of HIV in a region where nearly 15 million people are estimated to carry the virus -- 38 percent of the world's total.

But for many Batswana, as citizens of this landlocked desert country of 1.6 million call themselves, it is a strategy that has rarely been taught.

†¦ International experts long regarded Botswana as a case study in how to combat AIDS. It had few of the intractable social problems thought to predispose a country to the disease, such as conflict, abject poverty and poor medical care. And for the past decade, the country has rigorously followed strategies that Western experts said would slow AIDS.

With its diamond wealth and the largess of international donors, Botswana aggressively promoted condom use while building Africa's best network of HIV testing centers and its most extensive system for distributing the antiretroviral drugs that dramatically prolong and improve the lives of those with AIDS.

But even though the relentless pace of funerals began to ease in recent years, the disease was far from under control. The national death rate fell from the highest in the world, but only to second-highest, behind AIDS-ravaged Swaziland. Men and women in Botswana continued to contract HIV faster than almost anywhere else on Earth. Twenty-five percent of Batswana adults carry the virus, according to a 2004 national study, and among women in their early 30s living in Francistown, the rate is 69 percent.

Researchers increasingly attribute the resilience of HIV in Botswana -- and in southern Africa generally -- to the high incidence of multiple sexual relationships. Europeans and Americans often have more partners over their lives, studies show, but sub-Saharan Africans average more at the same time.

Nearly one in three sexually active men in Botswana reported having multiple, concurrent sex partners, as did 14 percent of women, in a 2003 survey paid for by the U.S. government. Among men younger than 25, the rate was 44 percent.

The distinction between having several partners in a year and several in a month is crucial because those newly infected with HIV experience an initial surge in viral loads that makes them far more contagious than they will be for years. During the three-week spike -- which ends before standard tests can even detect HIV -- the virus explodes through networks of unprotected sex.

This insight explained what studies were documenting: Africans with multiple, concurrent sex partners were more likely to contract HIV, and countries where such partnerships were common had wider and more lethal epidemics.

A model of multiple sexual relationships presented at a Princeton University conference in May showed that a small increase in the average number of concurrent sexual partners -- from 1.68 to 1.86 -- had profound effects, connecting sexual networks into a single, massive tangle that, when plotted out, resembles the transportation system of a major city.

†¦ These factors, researchers say, explain how North Africa, where Muslim societies require circumcision and strongly discourage sex outside monogamous and polygamous marriages, has largely avoided AIDS. They also explain why the epidemic is far more severe south of the Sahara, where webs of multiple sex partners are more common, researchers say.

Perhaps someone could correct me on this; do I have Landsbergs argument correct:

Yes, if low-infectivity sub-populations become more active sexually (with each other, or generally in the overall population? I'm not clear), then yes, risk-per-intercourse will decline, on average. Fair enough. But this is to seize completely the wrong metric, surely? It should be risk per man-day or total infections, and that will increase over the whole population. Each individual act will be safer, but as total acts will grow faster than risk-per-act will fall, overall the system is less safe.

Or have I misconstrued something?

Alistair, you aren't missing anything. According to Landsburg himself "reducing the rate of HIV transmission is in any event not the only social goal worth pursuing[...]What we really want is to minimize the number of infections resulting from any given number of sexual encounters; the flip side of this observation is that it is desirable to maximize the number of (consensual) sexual encounters leading up to any given number of infections". ( I don't think the phrase "if more people [...] had sex the AIDS epidemic could be reduced" describes Lansdburg proposition accurately.

John Pinkerton wrote:

A previous poster [Bob Murphy] says a "new equilibrium" will be established soon after an influx of previously abstainers, and then jumps to the conclusion that with more sexually active people, the new equilibrium will entail more infections.

Let me clarify: Of course, it is possible to reduce HIV cases by increasing the sexual activity of some people in society; Landsburg's hypothetical example demonstrates that, and it's possible Thailand illustrates it. (Though as others suggest, the reduction in HIV could be due to other factors like condom usage etc.)

What I am claiming is that this is a knife edge result. Just step back and think of what Landsburg is saying. There are sexually active people out there who are HIV+. So how can we reduce the number of people they give HIV to, over the next 12 months let's say?

Landsburg's reply is that we should encourage a bunch more people to get off the sidelines and start having sex.

It's true, the HIV+ people are less likely now to pass on the virus to someone who was originally promiscuous, because now there is more competition. But this doesn't prove the HIV+ people will go home alone more often now, because there are an influx of new people for them to hit on.

So again, if the goal is to reduce the total number of HIV cases (or even, to reduce the fraction of the population that has HIV), then you have to have pretty incredible initial conditions in order for the rule of "get more people to sleep around" to achieve results on that score.

In fairness to Landsburg, his goal isn't to minimize HIV cases, as others have pointed out above. But still, his titles and arguments sure sound as if that is his position, and that his results are fairly robust--rather than depending on initial scenarios where every guy visits the same 3 prostitutes.

Yikes. Pisani's example seems predicated on the fact that the only result which matters in a country where women are getting married later but having sex earlier is HIV rates.

Have we considered any of the other results of such a pattern, based on how that pattern has played out in other countries? What about, for instance, the economic consequences of declining fertility rates, which almost certainly follow from women and men marrying later? In fact, in Thailand, fertility rates are now at 1.6, which is below replacement rate. If you don't know what that means, see Phillip Longman's The Empty Cradle.

What about the divorce rate in Thailand, which has doubled since 1993? Might this also be a result of the sexual liberation of the rest of the country? What are its economic and cultural consequences? What about its consequences on the development and education of children?

One could go on, but the point is that this is an awfully narrow way to view a vast change in sexual habits.

Whatever caused the rise in premarital sex in Thailand between 1993 and "the end of the 1990s", surely it was not the booming Thai economy, as Pisani posits. There was, after all, the minor intervening matter of the 1997 Asian financial crisis, which in fact started with the collapse of the Thai baht. The Thai stock market fell 75%; naturally, a number of other countries were also severely affected.

But each woman having two partners isn't more sex, it's differently distributed sex. The real question is how much prostitute sex a low-partner woman has to displace before she lowers the HIV transmission rate. If a low-partner woman is a complete replacement for visiting prostitutes, it's quite possibly helpful. If she halves your rate of visiting prostitutes, it's debatable. If you visit prostitutes just as often, then you've just added another person to the epidemic.

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The solution to the AIDS problem in Africa is to do regular sexual health checks, and label the infected with a prominent marking. This would deter healthy people from having sex with those who carry the AIDS virus. This potentially could cause sex-starved AIDS patients to turn into rapists. A solution to this new problem would be to establish a network of AIDS victims, who could meet each other for fucking and solace. The End

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