English

Randomized experiments have become a popular tool in development economics research and have been the subject of a number of criticisms. This paper reviews the recent literature and discusses the strengths and limitations of this approach in theory and in practice. We argue that the main virtue of randomized experiments is that, owing to the close collaboration between researchers and implementers, they allow the estimation of parameters that would not otherwise be possible to evaluate. We discuss the concerns that have been raised regarding experiments and generally conclude that, although real, they are often not specific to experiments. We conclude by discussing the relationship between theory and experiments.

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Published Paper
Date:
September 01, 2008
English

This paper surveys evidence from recent randomized evaluations in developing countries on the impact of price on access to health and education. Debate on user fees has been contentious, but until recently much of the evidence was anecdotal. Randomized evaluations across a variety of settings suggest prices have a large impact on take-up of education and health products and services. While the sign of this effect is consistent with standard theories of human capital investment, a more detailed examination of the data suggests that it may be important to go beyond these models. There is some evidence for peer effects, which imply that for some goods the aggregate response to price will exceed the individual response. Time inconsistent preferences could potentially help explain the apparently disproportionate effect of small short-run costs and benefits on decisions with long-run consequences.

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Working Paper
Date:
August 01, 2008
English

The Millennium Development Goals call for reducing by half the proportion of people without sustainable access to safe drinking water. This goal was adopted in large part because clean water was seen as critical to fighting diarrheal disease, which kills 2 million children annually. There is compelling evidence that provision of piped water and sanitation can substantially reduce child mortality. However, in dispersed rural settlements, providing complete piped water and sanitation infrastructure to households is expensive. Many poor countries have therefore focused instead on providing community-level water infrastructure, such as wells. Various traditional child health interventions have been shown to be effective in fighting diarrhea. Among environmental interventions, handwashing and point-of-use water treatment both reduce diarrhea, although more needs to be learned about ways to encourage households to take up these behavior changes. In contrast, there is little evidence that providing community-level rural water infrastructure substantially reduces diarrheal disease or that this infrastructure can be effectively maintained. Investments in communal water infrastructure short of piped water may serve other needs and may reduce diarrhea in particular circumstances, but the case for prioritizing communal infrastructure provision needs to be made rather than assumed.

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Working Paper
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May 01, 2007
English

This paper is a practical guide (a toolkit) for researchers, students and practitioners wishing to introduce randomization as part of a research design in the field. It first covers the rationale for the use of randomization, as a solution to selection bias and a partial solution to publication biases. Second, it discusses various ways in which randomization can be practically introduced in a field settings. Third, it discusses designs issues such as sample size requirements, stratification, level of randomization and data collection methods. Fourth, it discusses how to analyze data from randomized evaluations when there are departures from the basic framework. It reviews in particular how to handle imperfect compliance and externalities. Finally, it discusses some of the issues involved in drawing general conclusions from randomized evaluations, including the necessary use of theory as a guide when designing evaluations and interpreting results.

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Report
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December 01, 2006
English

This paper argues that the important challenge for an impact evaluation study is to determine the answer to the question how lives of participants would have changed had the policy not been implemented. An evaluation that provides an answer to be above question can be considered as a reliable evaluation.

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Brief
Date:
August 01, 2006
English

This paper presents an application of the randomized controlled trial methodology to evaluating modifications to the design of microcredit programs. As microfinance becomes an even more popular tool for fighting poverty, institutions innovate in their products and programs at a rapid pace. Policymakers and practitioners should know the relative impact of different designs, both to the client (in terms of welfare) and to the institution (in terms of financial sustainability). We discuss the current approach to evaluating product or program changes, and the reasons why more rigorous evaluations are necessary. We then discuss why randomized controlled trials can prove vital to icrofinance institutions in identifying effective program designs in different environments. In this paper, we focus on the choice of lending methodologies – credit with education versus credit only, and group versus individual liability -- to illustrate the benefits of randomized controlled trials as a business tool for measuring impact and learning how to improve sustainability and growth. This methodology can be employed for a plethora of program design issues, such as timing of payments, loan size, interest rates, term, and other services such as insurance and savings.

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Working Paper
Date:
July 01, 2006

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