Kremer: Harvard University, The Brookings Institution, The Center for Global Development, and the University of California, Berkeley and National Bureau of Economic Research (NBER); Miguel: University of California (NBER)

Published in the Quarterly Journal of Economics (Volume 112, Number 3, Pages 1007-1065), this paper shares the details of a randomised evaluation of a Kenyan deworming programme in an effort to estimate peer effects in technology adoption and to shed light on foreign aid donors' movement toward sustainable community provision of public goods.

This study explores the process of social learning using data from a programme which promoted the use of de-worming medicine in Kenyan schools. The Primary School Deworming Project (PSDP) was carried out by a Dutch non-governmental organisation (NGO) called ICS Africa, in cooperation with the Kenyan Ministry of Health. It took place in 75 schools in Busia district, an economically poor and densely settled farming region in western Kenya. In addition to medical de-worming treatment, the project included intensive health education on worm prevention behaviours - washing hands, wearing shoes, and avoiding infected fresh water - which was provided by both teachers and adult NGO workers using culturally appropriate materials designed in Tanzania.

In the paper, the authors "develop a simple framework in which people adopt deworming if expected private benefits exceed the expected cost....People are linked in a social network and receive signals about adoption, drug effectiveness, and how to use the drugs." An excerpt from the report, which follows, provides a look at the central findings from the research:

"In this study we find that, first, the introduction of a small fee for deworming drugs ('cost-sharing') led to an 80 percent reduction in treatment rates, consistent with the hypothesis that people have low private valuation for deworming. Take-up dropped sharply when going from a zero price to a positive price but was not sensitive to the exact (positive) price level, suggesting that it may be particularly counter-productive to charge small positive prices for the treatment of infectious diseases. Second, an intensive school health education intervention had no impact on worm prevention behaviors. Third, a verbal commitment 'mobilization' intervention - in which people were asked in advance whether they planned to take deworming drugs... - had no impact on adoption.

We also examine peer effects in adoption....We collect data on the network structure of links between school communities and use this to empirically estimate the impact on adoption decisions not only of individuals' direct social links, but also of higher-order social links....[W]e allow survey respondents to specify their social links themselves and estimate the impact of learning through different types of links. We then simulate the impact of alternative ways of seeding the new technology given the observed network structure of links across schools in our sample. We find that additional social links to early treatment schools reduce the probability that children take deworming drugs and increase the probability that parents say that deworming drugs are 'not effective.' This negative take-up result holds both for direct social links and for indirect second order connections....The lower take-up among those with more knowledge may be due to the high proportion of deworming benefits flowing not to the treated child or her family, but to others in the local community....People may only have realized how much of the benefits were external as they gained experience with the program. Negative social effects on take-up are especially large empirically for families with more schooling, a group who start out with particularly favorable beliefs about the technology but then rapidly revise their beliefs downwards as they acquire more information.

Our results...suggest that, at least in this context, peer effects due to imitation or due to learning about how to use the technology are small....[I]t is probably an illusion to think that a onetime infusion of external assistance will lead to the indefinitely sustainable voluntary provision of most local public goods. There may simply be no alternative to ongoing subsidies..."