Altruism in preventive health behavior: At-scale evidence from the HIV/AIDS pandemic.

Preventive behavior with regards to disease transmission offers a promising context in which to provide empirical evidence on altruism in human populations. I examine the association between HIV status, own knowledge about status, and preventive health behavior using household survey data from over 200,000 individuals in 25 sub-Saharan African countries. I find that individuals who are HIV positive and have taken a standard HIV test are much more likely to engage in efforts to prevent HIV transmission than are individuals who are HIV negative and have taken a standard HIV test. Moreover, this difference is greater than the difference between HIV positives and HIV negatives for individuals who have not taken a standard HIV test. Consistent with an altruistic motivation, this double-difference is larger for individuals who are married than for individuals who are not married. These results appear to be the first evidence on the change in risky sexual behavior associated with HIV testing at scale and are consistent with altruism dominating any self-interested response to HIV testing.