Timing and Duration of Exposure in Evaluations of Social Programs

42 Pages Posted: 20 Apr 2016

See all articles by Elizabeth King

Elizabeth King

World Bank - Development Research Group (DECRG)

Jere Behrman

University of Pennsylvania - Department of Economics

Multiple version iconThere are 2 versions of this paper

Date Written: August 1, 2008


Impact evaluations aim to measure the outcomes that can be attributed to a specific policy or intervention. Although there have been excellent reviews of the different methods that an evaluator can choose in order to estimate impact, there has not been sufficient attention given to questions related to timing: How long after a program has begun should one wait before evaluating it? How long should treatment groups be exposed to a program before they can be expected to benefit from it? Are there important time patterns in a program's impact? Many impact evaluations assume that interventions occur at specified launch dates and produce equal and constant changes in conditions among eligible beneficiary groups; but there are many reasons why this generally is not the case. This paper examines the evaluation issues related to timing and discusses the sources of variation in the duration of exposure within programs and their implications for impact estimates. It reviews the evidence from careful evaluations of programs (with a focus on developing countries) on the ways that duration affects impacts.

Keywords: Primary Education, Health Monitoring & Evaluation, Poverty Monitoring & Analysis, Education For All, ICT Policy and Strategies

Suggested Citation

King, Elizabeth and Behrman, Jere R., Timing and Duration of Exposure in Evaluations of Social Programs (August 1, 2008). World Bank Policy Research Working Paper No. 4686, Available at SSRN: https://ssrn.com/abstract=1233062

Elizabeth King (Contact Author)

World Bank - Development Research Group (DECRG) ( email )

1818 H. Street, N.W.
Washington, DC 20433
United States

Jere R. Behrman

University of Pennsylvania - Department of Economics ( email )

Ronald O. Perelman Center for Political Science
133 South 36th Street
Philadelphia, PA 19104-6297
United States
215-898-7704 (Phone)
215-573-2057 (Fax)

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