RAND Review
Perspectives
Plots and Curves
What Mexican Sex Workers Can Teach Economists About Preventing HIV
SINCE THE HUMAN IMMUNODEFICIENCY virus (HIV) was first discovered in the early 1980s, 23 million people have died from it worldwide. Every day, nearly 20,000 people become infected. One of the major global sources of infection, in addition to intravenous drug use, is having unprotected sex with a sex worker.
Although using condoms can protect against HIV infection, condoms work only if they are used consistently. In Armenia, where HIV is rampant, only 10 percent of sex workers reported using condoms consistently. It is therefore not surprising that interventions worldwide have homed in on educating sex workers about the risk of HIV and the importance of using condoms.
Compared with Armenia, Mexico is a success story. Thanks to a massive public education campaign aimed at sex workers and their clients since the late 1980s, HIV prevalence among sex workers in Mexico is very low — less than 1 percent — and condom use is very high — around 80 percent. Despite this success, the government is still concerned about a potential outbreak and is considering a new education campaign targeted at sex workers.
But would an additional educational campaign directed at the same population make much of an improvement? This is the question addressed in a talk at RAND by Paul Gertler, professor of economics and public policy at the University of California, Berkeley.
 Mexico City prostitutes march in a candlelight procession in memory of their fellow workers who have died from the AIDS virus. The annual ceremony, held around the "day of the dead" festivities, tries to promote safe sex and an awareness of the spread of HIV in Mexico. |
Sex on Demand
Commercial sex is a business, one that has a supply side (sex workers) and a demand side (clients). As Gertler notes, most interventions focus on the supply side — educating sex workers, making it easier for them to get inexpensive condoms, increasing their negotiating skills, and creating safe and supportive work environments.
Gertler agrees that such a focus is effective (and necessary), but he argues that all the attention on the supply side ignores the demand side of the equation. Clients sometimes request sex without condoms and are willing to pay more for it. If they offer to pay enough, will sex workers — including the ones who know about the importance of using condoms and who would otherwise want to use them — decide that the risk of getting HIV is low enough to be worth taking?
To answer this question, Gertler surveyed more than a thousand sex workers in two Mexican states — Morelos, one of the country’s poorer states, and Michoacan, one of the wealthier ones — about their last three or four transactions. In earlier focus groups with sex workers and their clients, he found that the commercial sex business operates pretty much how people think it operates: The client and sex worker bargain with each other, with the client trying to determine price and services and the sex worker trying to gauge willingness to pay and service preferences. Most important, at least in Mexico, such negotiations routinely include a discussion of condom use.
In the survey, sex workers confirmed that condom use is widespread in Mexico. Eighty-three percent said they used condoms in all their transactions, while an additional 12 percent said they used condoms some of the time. But of most interest is who suggested using or not using condoms.
When condoms were used, Gertler explained, 95 percent of the time it was because sex workers had suggested it. When condoms were not used, 68 percent of the time it was because clients had requested it. There appears to be little question that demand-side pressures contribute to the small but continuing problem of not using condoms.
If the Price Is Right
When sex workers agree to have unprotected sex upon request, Gertler found, they do so because the price for doing so is right, meaning that clients are willing to pay a premium. How high a premium? Based on his analysis, sex workers received an average of 23 percent more for unprotected sex (and up to 46 percent more if the workers were judged to be especially attractive).
The market works both ways. If clients suggest using condoms, then the clients pay 8 percent more for protected sex. And if sex workers are the ones who request sex without a condom, then they have to give clients a 20 percent discount. But unprotected sex usually comes at the client’s request.
 Ilda, a young prostitute working the "red light" district of Tijuana, Mexico, displays her health record book, which she is required to carry by law. |
Reducing the small percentage of transactions in Mexico that still don’t involve the use of condoms will require a demand-side solution, Gertler argues. One obvious alternative would be to educate clients about the need to use condoms—about the “joy of safe sex” — but trying to identify and educate clients would be difficult and prohibitively expensive.
Gertler proposes a more novel option: Use financial incentives to induce sex workers to use condoms. In other words, exploit the nature of the free market, and compensate sex workers for the money they would otherwise earn by agreeing to have unprotected sex. Fight demand with demand.
To do so, Gertler suggests relying on the “health certificate” that all sex workers must carry in Mexico (and, for that matter, in most of Latin America). In these countries, sex workers must periodically pay to be tested for HIV and sexually communicable diseases and to receive a certificate proving they are “clean.”
Such testing is expensive. But if the costs of the test are set precisely to match the premium that sex workers earn for unprotected sex — and if the sex workers who test clean can have their costs ultimately reimbursed — then the sex workers may be more likely to choose not to have sex without a condom. The Mexican government is considering a pilot test of such a program.
Education and Earnings
For countries like Mexico — where a massive public education program has been in place for years, where sex workers understand the dangers of HIV and the need for condom use, and where the prevalence of HIV remains low — the implications of the findings are clear: Focusing on the demand side of the equation makes sense.
But the work has broader implications for all countries. Education targeted at sex workers is certainly necessary, especially in countries like Armenia that have a high prevalence of HIV and low condom use. But education has its limits—“diminishing returns,” as Gertler contends. Demand-side pressure from clients will ensure that there are always cases where condoms aren’t used, despite excellent educational efforts. Therefore, every country should use complementary interventions that focus both on supply and on demand.
On the supply side, countries need to educate sex workers, increase their access to inexpensive condoms, and empower them. On the demand side, countries need to try a number of options, such as providing financial incentives to induce sex workers to use condoms all the time. 
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