Why Don't People Take Their Medicine? Experimental Evidence from Kenya
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Why Don’t People Take their Medicine? Experimental Evidence from Kenya Edward Miguel* University of California, Berkeley Michael Kremer Harvard University November 2002 Abstract: The standard public finance approach to health care in less developed countries involves identifying and heavily subsidizing priority health interventions that generate treatment externalities (e.g., vaccines). A popular recent approach instead argues that health education, community mobilization, and cost-recovery are also necessary for successful programs. We focus on the case of intestinal worms – which affect one in four people worldwide – and provide evidence from a series of randomized evaluations that subsidies are more effective than other factors in influencing deworming drug take-up among schoolchildren in Kenya. An effort to educate children on worm prevention was ineffective at changing behavior. Those who were randomly exposed to more information about the deworming drugs through their social networks were significantly less likely to take them. A verbal commitment “mobilization” intervention from social psychology led to significantly lower treatment rates. In contrast, drug take-up was highly sensitive to cost: the introduction of a small fee led to a massive eighty percent reduction in treatment rates (relative to free treatment). Cost-sharing appears particularly inappropriate for medical conditions characterized by large treatment externalities – like worms and other infectious diseases. The results suggest that, to promote new health technologies in less developed countries, scarce public resources should be focused on subsidies. * Contact: Edward Miguel ([email protected]) or Michael Kremer ([email protected]). The authors thank ICS Africa and the Kenya Ministry of Health, Division of Vector Borne Diseases for their cooperation in all stages, and would especially like to acknowledge the contributions of Elizabeth Beasley, Laban Benaya, Simon Brooker, Pascaline Dupas, Alfred Luoba, Sylvie Moulin, Robert Namunyu, Polycarp Waswa, Peter Wafula, and the entire PSDP field staff and data group, without whom the project would not have been possible. Gratitude is extended to the teachers, school children, and households of Busia for participating in the study. Melissa Gonzalez-Brenes and Tina Green have provided excellent research assistance. We thank George Akerlof, Guido Imbens, Botond Koszegi, David Laibson, Kaivan Munshi, Mark Rosenzweig, and Chris Udry for helpful conversations. We are grateful for financial support from the World Bank, the NIH Fogarty International Center (R01 TW05612-02), and U.C. Berkeley Center for Health Research. All errors are our own. 1. Introduction Under a standard public finance approach, central government public health policy makers in less developed countries identify and heavily subsidize cost-effective public health interventions that generate positive treatment externalities. The successful national childhood vaccination campaigns of past decades serve as a model for such efforts. An alternative approach argues that intensive health education and local community mobilization – as well as cost-recovery from beneficiaries to finance these activities – are also necessary for successful public health programs. This split on the design of public health programs runs through World Bank reports on health policy (World Bank 1993, 1994, 2002).1 Yet little rigorous work has examined the impact of such efforts on health technology adoption, and their cost-effectiveness remains unproven. We report on a series of randomized evaluations designed to promote deworming drug adoption in an area of rural Kenya where over 90 percent of school children suffer from intestinal worm infections. Worm infections also affect one in four people worldwide, and school-based mass treatment of worms was identified among the most cost-effective health interventions in the 1993 World Development Report (World Bank 1993). In a previous study, within the context of a randomized evaluation, we found that deworming drugs are highly effective at improving health and certain educational outcomes (Miguel and Kremer 2001). Still a large minority of children opted not to receive free treatment through the program.2 The empirical results in this paper indicate that increasingly popular public health approaches relying on health education, community mobilization, and cost-recovery may fail, and may even backfire and lead to lower drug treatment rates in a rural African setting. Cost-sharing appears 1 To illustrate, a recent World Bank (2002) report on water provision advocates the second approach, advising ministry of health officials: “Don’t provide hardware (water pipes and latrines) without the software (hygiene promotion) and community training and organization to sustain/maintain services.” 2 Technology adoption is central to the study of economic growth and development, especially related to the adoption of health, family planning, and agricultural technologies. Many health-related anomalies have been studied, including slow adoption of the flu vaccine and beta-blockers in the United States (Schneider et al. 2001, Krumholz et al. 1998), water boiling in Peru, the use of well water rather than stream water in Egypt (Rogers 1995), and safer sexual behavior during the AIDS epidemic (Philipson and Posner 1995). 1 particularly inappropriate for medical conditions characterized by large treatment externalities – like worms and other infectious diseases. In the remainder of this section we describe our other main finding, on social learning about deworming drugs. 1.1 Health Education and Social Learning Intestinal worm infections can be reduced in several different ways. One approach emphasizes medical treatment with low cost and safe deworming drugs, while others have argued that a more sustainable approach also addresses the root causes of worm infection – which lie in poor hygiene – rather than simply using the “silver bullet” solution of medication (especially since re-infection is rapid and people must be treated twice per year with drugs to remain largely worm-free). We find that the original deworming program’s intensive school health education efforts had no impact on worm prevention behaviors over a year after the start of the program (Miguel and Kremer 2001). Of course, examining only “direct” health education impacts maybe misleading if health education has its biggest impacts by influencing the behavior of the social contacts of those who receive health education, through a process of social learning, but given that there was no direct health education effect in this setting, prevention behaviors are unlikely to have diffused to others. However, we are able to explore a different aspect of social learning – learning about the deworming drugs themselves. It has been hypothesized that inadequate information on new technologies is a primary cause of slow adoption (Rogers 1995). The estimation of information social effects in this paper relies on the experimental design of the original deworming treatment program. The “early treatment” schools and “late treatment” schools were randomly selected, producing exogenous local variation in the proportion of individuals eligible for the deworming program. We then collected survey data on social networks and explore how exogenous variation in exposure to the deworming drugs through social contacts affected individuals’ own adoption decisions. The experimental identification of social effects is the main methodological contribution of this study. 2 Children whose parents have randomly more social links to early treatment schools in rural Kenya are themselves significantly less likely to take deworming drugs in 2001: for each additional social link that a parent has to an early treatment school, her child is 3.2 percentage points less likely to take deworming drugs in 2001. This suggests that individuals with more exposure to the project learn not to take deworming drugs despite their benefits – an apparent case of failed social learning. However, a simple learning model with rational agents is consistent with these seemingly anomalous findings. If individuals have prior beliefs on drugs benefits that are too “optimistic” – in the sense of expecting very large health gains from deworming – then additional information lowers posterior beliefs and drug take-up rates. In previous work, we found that mass deworming treatment leads to substantial externality health benefits for individuals near treated schools, since mass treatment reduces disease transmission and subsequent re-infection. These large externalities provide a plausible explanation for relatively low drug take-up, since they dramatically reduce private benefits to deworming and thus may have led people to hold overly optimistic priors (for instance, if people expected private benefits to be as large as they would have been in the absence of externalities). More broadly, the results indicate that social learning may fail to generate high drug adoption rates for diseases characterized by large treatment externalities, and that large subsidies may be necessary to increase take-up. This is likely to be especially important for Africa, where half of the disease burden is associated with infectious and parasitic disease (WHO 1999). 1.2 The structure of this paper The remainder of the paper is structured as follows. Section 2 discusses medical aspects of worm infections, and competing health paradigms in rural western Kenya,