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American Economic Review Vol. 105 No. 5 2015

Learning from Experiments when Context Matters

Lant Pritchett1; Justin Sandefur2

1 Harvard Kennedy School, 79 JFK Street, Cambridge, MA 01238, and Center for Global Development, (e-mail: ) · 2 Center for Global Development, 2055 L Street NW, Washington, DC 20036 (e-mail: )

Abstract

Suppose a policymaker is interested in the impact of an existing social program. Impact estimates using observational data suffer potential bias, while unbiased experimental estimates are often limited to other contexts. This creates a practical trade-off between internal and external validity for evidence-based policymaking. We explore this trade-off empirically for several common policies analyzed in development economics, including microcredit, migration, and education interventions. Based on mean-squared error, non-experimental evidence within context outperforms experimental evidence from another context. This advantage declines, but may not reverse, with experimental replication. We offer four reasons these findings are of general relevance to policy evaluation.

DOI
10.1257/aer.p20151016
Volume
105
Issue
5
Pages
471-475
Language
en
Sources
bibtex:phds-export.bib openalex crossref

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