A new data set facilitates study of learning spillovers in World War II shipbuilding. Our results contain two principal but contrasting themes. First, learning spillovers were a significant source of productivity growth, and may have contributed more than conventional learning effects. Second, the size of the learning externalities across yards, as measured by Spence's θ, were small. These findings, which are not mutually inconsistent, suggest an optimistic view of learning spillovers: they are a significant source of productivity growth, but the market failures induced by learning externalities may be modest.

This paper evaluates an experiment in which individuals in rural Malawi were randomly assigned monetary incentives to learn their HIV results after being tested. Distance to the HIV results centers was also randomly assigned. Without any incentive, 34 percent of the participants learned their HIV results. However, even the smallest incentive doubled that share. Using the randomly assigned incentives and distance from results centers as instruments for the knowledge of HIV status, sexually active HIV-positive individuals who learned their results are three times more likely to purchase condoms two months later than sexually active HIV-positive individuals who did not learn their results; however, HIV-positive individuals who learned their results purchase only two additional condoms than those who did not. There is no significant effect of learning HIV-negative status on the purchase of condoms.

This paper demonstrates the acute sensitivity of education program effectiveness to the choices of inputs and outcome measures, using a randomized evaluation of a mother-tongue literacy program. The program raises reading scores by 0.64 SD and writing scores by 0.45 SD. A reduced-cost version instead yields statistically insignificant reading gains and some large negative effects (−0.33 SDs) on advanced writing. We combine a conceptual model of education production with detailed classroom observations to examine the mechanisms driving the results; we show they could be driven by the program initially lowering productivity before raising it, and potentially by missing complementary inputs in the reduced-cost version.

An individual who takes an HIV test can be informed about their own status and risk. Similarly, when friends, family or neighbors learn of a person's HIV status, they may update their beliefs about HIV infection among people they know. Using an experiment conducted in rural Malawi which randomly assigned incentives to learn HIV results, we find that as people in the community learn their HIV results, individuals revise their beliefs downward about deaths attributable to HIV/AIDS. We find corresponding behavioral responses with a significant decrease in condom use and no significant increase in multiple partnerships among those who are HIV-negative.

Understanding behavioral responses to changes in actual or perceived risk is important because risk-reduction goals can be undermined by risk-compensating behavior. This paper examines the response to new information about the risk of HIV infection. Approximately 1,200 circumcised and uncircumcised men in rural Malawi are randomly informed that male circumcision reduces the HIV transmission rate, predicting asymmetric behavioral responses. We find no evidence that the information induces circumcised men to engage in riskier sex while uncircumcised men practice safer sex in response to the information. There were no significant effects of the information on child circumcisions after one year.