Chong et al.

20 the novelty of this approach is that it provides strong evidence that anonymity and confidentiality of information technologies may be of great use in segments of the society in which keeping such anonymity is difficult to overcome.<sup>28</sup> The results on knowledge and attitudes are important because these two factors have been shown to be the strongest protective factors in preventing STIs, HIV, and pregnancy among teens (Kirby, Lepore, and Ryan 2007). Furthermore, recent research has documented the important role that social norms play in responsible sexual behavior (Munshi and Myaux 2005; Ashraf, Field, and Lee 2014). By changing knowledge and attitudes in youth attending school, sexual education can ultimately play a fundamental role in achieving desirable aggregate changes in sexual behavior.

A second contribution to the sexual health education literature is the focus on spillovers, through a twostage experimental design. The results indicate that spillovers from treated to untreated classrooms in the same school are negligible.

Lastly, the analysis provides strong indications that effects of the course were reinforced when treated individuals had larger percentages of their friend networks in treatment classrooms. The evidence is robust across a large set of sexual health attitude and knowledge indicators. In particular, the analysis found that students whose networks were more intensely treated had significant improvements in knowledge and attitudes, which the study interprets as social reinforcement effects or complementarities. These results demonstrate the positive externalities of the public provision of sex education: When an individual takes a sex education course, this decision has positive effects on sexual health outcomes among his or her close friends. This suggests that without collective action, there is an underprovision of sex education.

These results provide an optimistic assessment of the use of information technologies to generate improved sexual health outcomes among the youth. The cost-benefit analysis suggests that because Internetbased sexual health education programs are extremely low cost, their benefits in terms of STI reductions actually justify the costs.

# **References**

AIDS Control and Prevention Project (AIDSCAP). 1997. _Making Prevention Work: Global Lessons Learned from the AIDS Control and Preventional Project 1991–1997._ Arlington, VA: Family Health International.

Angrist, J., and V. Lavy. 2002. “New Evidence on Classroom Computers and Pupil Learning.” _Economic Journal_ 112 (482): 735–65.

Ashraf, N., E. Field, and J. Lee. 2014. “Household Bargaining and Excess Fertility: An Experimental Study in Zambia.” _American Economic Review_ 104 (7): 2210–37.

Auriol, E., and M. Wartlers. 2012. “The Marginal Cost of Public Funds and Tax Reform in Africa.” _Journal of Development Economics_ 97 (1): 58–72.

Barrera-Osorio, F., and L. L. Linden. 2009. “The Use and Misuse of Computers in Education: Evidence from a Randomized Controlled Trial of a Language Arts Program.” Policy Research Working Paper No. 4836, World Bank, Washington, DC.

Brener, N. D., J. O. G. Billy, and W. R. Grady. 2003. “Assessment of Factors Affecting the Validity of Self-Reported Health-Risk Behavior Among Adolescents: Evidence from the Scientific Literature.” _Journal of Adolescent Health_ 33 (6): 436–57.

Brent, R. J. 2011. “An Implicit Price of a DALY for Use in Cost Benefit Analysis of ARVs.” _Applied Economics_ 43 (11): 1413–21.

Bruhn, M., and D. McKenzie. 2009. “In Pursuit of Balance: Randomization in Practice in Development Field Experiments.” _American Economic Journal: Applied Economics_ 1 (4): 200–32.

- 28 This approach provides an alternative to social marketing campaigns that attempt to increase the use of condoms in developing countries, and may be better suited than the latter for the segments of the population described in this paper. Among others, in Tanzania, a campaign to promote condom use among women was entitled “Talk to Him” and included posters and depicting a variety of confident, empowered, young women (AIDS Control and Prevention Project 1997).