Increased HIV risk creates incentives for people with low sexual activity to reduce their activity, but may make high-activity people fatalistic, leading them to reduce their activity only slightly, or actually increase it. If high-activity people reduce their activity by a smaller proportion...

Under asymmetric information about sexual history, sexual activity creates externalities. Abstinence by those with few partners perversely increases the average probability of HIV infection in the pool of available partners. Since this increases prevalence among the high activity people who...

The authors report results from a randomized evaluation comparing three school-based HIV/AIDS interventions in Kenya: (1) training teachers in the Kenyan Government's HIV/AIDS-education curriculum; (2) encouraging students to debate the role of condoms and to write essays on how to protect...