which is a more accurate measure of the epidemic. Another interesting feature of the data set is that it not only contains the results of yearly anonymous HIV testing in the population, but it also includes information about the mechanisms leading to HIV infection, in particular sexual behavior such as condom use and the number of partners.

One limitation of the analysis, however, is that there is no control group, as all surveyed villages were exposed to the information campaign. In order to contrast different levels of exposure to the information, this paper will rely instead on a distinction based on the birth cohort of the individuals and the period of observation. In particular, the paper compares those who started their sexual life before the arrival of the information and those who initiated their sexual activity afterward. The paper further compares HIV outcomes for the better and the less well-educated in the population.

The analysis indicates that, over the past decade, there has been a substantial evolution in the HIV prevalence/education gradient among the population in rural Uganda surveyed by the GPC. Early in the epidemic, in 1990, there is no signi fi cant relationship between education and HIV prevalence. In 2001, after more than a decade of information and prevention efforts about the dangers of the epidemic, for individuals who started their sexual life after the start of the prevention campaign, the higher the education level, the lower the risk of being HIV positive. This effect is mainly concentrated among females.

This paper seems to be one of the fi rst to report robust evidence that for young cohorts in Africa there is now a negative gradient between education and HIV infection, suggesting that the effect of education only emerges over time.<sup>1</sup> As illustrated in fi gure 1, between 1990 and 2000, the HIV prevalence for young individuals with no education or primary education decreased by 6 percentage points, while it decreased by 12 percentage points for individuals who went to secondary school. Results from a study of HIV incidence in a duration framework con fi rm this fi nding by showing

> 1 Out of 27 studies reviewed by Hargreaves and Glynn (2002), only one, among sugar estate workers in Ethiopia, reported a signi fi cantly negative association between HIV infection and education. Most of these studies, however, are in urban settings and based on data collected in the beginning of the 1990s, at an earlier stage of the epidemic. Fylkesnes and others (2001) also has evidence of a negative relationship between HIV infection and education in urban Zambia. For other studies of the relationship between HIV prevalence and education see Blanc (2000); Gregson, Waddell, and Chamdiwana (2001); Kilian and others (1999); Vandemoortele and Delamonica (2001). The economic profession has mainly addressed the HIV/AIDS epidemic by looking at its demographic and economic consequences (Ainsworth, Beegle, and Koda 2000; Clark and Vencatachellum 2003; Garnett, Grossly and Gregson 2001; Lundberg and Over 2000; Over 1997), by investigating the compensating differential for condom use (Gertler, Shah and Bertozzi 2003; Rao and others 2003) or by studying the issue of the affordability of the treatment and the incentives to create a vaccine (Kremer 2000).

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