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Title:Sample attrition bias in randomized experiments: a tale of two surveys PDF Logo
Authors:Behaghel, Luc
Crépon, Bruno
Gurgand, Marc
Le Barbanchon, Thomas
Issue Date:2009
Series/Report no.:IZA discussion papers 4162
Abstract:The randomized trial literature has helped to renew the fields of microeconometric policy evaluation by emphasizing identification issues raised by endogenous program participation. Measurement and attrition issues have perhaps received less attention. This paper analyzes the dramatic impact of sample attrition in a large job search experiment. We take advantage of two independent surveys on the same initial sample of 8,000 persons. The first one is a long telephone survey that had a strikingly low and unbalanced response rate of about 50%. The second one is a combination of administrative data and a short telephone survey targeted at those leaving the unemployment registers; this enriched data source has a balanced and much higher response rate (about 80%). With naive estimates that neglect non responses, these two sources yield puzzlingly different results. Using the enriched administrative data as benchmark, we find evidence that estimates from the long telephone survey lack external and internal validity. We turn to existing methods to bound the effects in the presence of sample selection; we extend them to the context of randomization with imperfect compliance. The bounds obtained from the two surveys are compatible but those from the long telephone survey are somewhat uninformative. We conclude on the consequences for data collection strategies.
Subjects:Randomized evaluation
survey non response
bounds
JEL:C31
C93
J68
Persistent Identifier of the first edition:urn:nbn:de:101:1-20090605191
Document Type:Working Paper
Appears in Collections:IZA Discussion Papers, Forschungsinstitut zur Zukunft der Arbeit (IZA)

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