There is a well-known phenomenon that states that when an activity becomes safer, people will respond with riskier behavior. The classic example is the use of seat belts that has lead to more aggressive driving (although there is a claim that this example is wrong). Now switch to another risky behavior: sex. It is well established that male circumcision leads to a significantly lower transmission probability of AIDS. Is risk compensation also happening here?
Nicholas Wilson, Wentao Xiong and Christine Mattson look at recently circumcised males in a region of Kenya and find that their sex behavior is less risky than the uncircumcised control group. This is not a selection effect, as circumcision has been randomly assigned. The authors think that the circumcised ones have become less fatalist about future life prospects and thus changed their behavior for the better (this is also why you want to provide health insurance conditional on not dying from AIDS). I wonder though whether the circumcision has made them more aware of the risk of AIDS as well.