'Shopping' for a mate is costly in Sub-Saharan Africa
Why are African HIV rates so high?
A little know fact about HIV is that the transmission rate of the disease from an infected individual to their sexual partner is surprisingly low. For example, the chance that you are infected with HIV during vaginal intercourse with an already infected individual is about one in a thousand. Having sex with that person for a whole year exposes you to a chance of about 8-12 per cent of being infected yourself.
So, how is it that a disease that is so difficult to transmit has managed to infect so many in Africa, where the infection rate for some populations is as high as 40 per cent?
It may be tempting for those of us in the West to believe that the prevalence of HIV in Africa is related to high rates of promiscuity and commercial sex, but there is compelling new evidence by economist Jeremy Magruder at Berkley University that the high rate of the disease can be explained by behaviour that we all engage in -- shopping for a mate.
In brief, his argument goes like this. Women and men experience a brief period in their lives while searching for the right marriage partner in which they are in a series of monogamous relationships with high turnover. This searching behaviour generates a constant pool of individuals in short-term relationships. Rates of HIV transmission may be low on average, but the probability of transmission from a person who has become recently infected is as much as 10 times higher. So, introduce one recently infected person into this pool of people who are searching for a mate and the whole pool are at risk of being infected.
The paper finds that the introduction of one person per hundred into a searching pool will lead to an HIV prevalence similar to that in Kenya or Tanzania. The introduction of just three infected people per hundred into the searching pool will lead to South Africa's epidemic prevalence rates. Only a small fraction of sexually active people need to be engaging in risky behaviours in order to create the pandemic despite low transmission rates.
So why are so many women infected with HIV in Sub-Saharan Africa compared to the West, where women engage in the same type of searching behaviour? The difference is that in Western countries a sufficient number of people in the marital searching pool use condoms in short term relationships.
The important policy implication here is that reducing HIV prevalence in Africa to North America levels would not require a major change in African social norms nor would it require a major medical intervention. It doesn’t even require that 100 per cent of single people searching for a mate use condoms during sex. The economic model suggests that if only 50 per cent of the participants in the marital searching pool use condoms for the first three months of their relationships, prevalence rate would drop to those comparable to the West.
Perhaps you are thinking that telling people to use condoms during sex to prevent infection is hardly news. The problem is that current health campaigns tell people in Africa that they have to use condoms for the rest of their lives, even after they are married. If you knew that there was no way you were going to do that (how many people would?) and you believed that the risk of infection in the future was the same as it is now, then why use one today?
The alternative policy would be to convince people to use condoms in the first three months of new sexual relationships. Give them an achievable goal rather than the unrealistic goal of saying that they must never have sex without a condom. This won’t eliminate HIV infections but it could encourage better choices at the beginning of relationships when the risks are highest.
If it isn’t promiscuity that is killing women in Africa, but shopping for a mate, then this small change in behaviour could be what is needed to save the lives of millions of women and children.