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Robustness of the Encouragement Design in a Two-Treatment Randomized Control Trial


  • Behaghel, Luc

    () (Paris School of Economics)

  • Crépon, Bruno

    () (CREST)

  • Gurgand, Marc

    () (Paris School of Economics)


In this paper we discuss how the "encouragement design" used in randomized controlled trials can be extended to a setting with two treatments and one control group. Conditions to interpret the Two-Stage Least Squares (TSLS) estimates causally are stronger than in the case with only one treatment and one control group. A first case where a causal interpretation holds is when only those assigned to one of the two treatments can effectively enter the corresponding program. A second case is when there are always takers. In that second case, entry rates into a given program should be the same among those assigned to the control group and those assigned to the other program; this restriction can be tested from the data. In cases where the restriction is rejected, we derive bounds to the Local Average Treatment Effect (LATE) based on weaker monotonicity conditions. We illustrate the results using data from a large randomized experiment where job seekers at risk of long term unemployment can receive a reinforced counseling scheme offered either by the public or the private sector, or remain on a standard track.

Suggested Citation

  • Behaghel, Luc & Crépon, Bruno & Gurgand, Marc, 2013. "Robustness of the Encouragement Design in a Two-Treatment Randomized Control Trial," IZA Discussion Papers 7447, Institute for the Study of Labor (IZA).
  • Handle: RePEc:iza:izadps:dp7447

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    References listed on IDEAS

    1. Luc Behaghel & Bruno Cr?pon & Marc Gurgand, 2014. "Private and Public Provision of Counseling to Job Seekers: Evidence from a Large Controlled Experiment," American Economic Journal: Applied Economics, American Economic Association, vol. 6(4), pages 142-174, October.
    2. David S. Lee, 2009. "Training, Wages, and Sample Selection: Estimating Sharp Bounds on Treatment Effects," Review of Economic Studies, Oxford University Press, vol. 76(3), pages 1071-1102.
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    Cited by:

    1. Lars Kirkebøen & Edwin Leuven & Magne Mogstad, 2014. "Field of Study, Earnings, and Self-Selection," NBER Working Papers 20816, National Bureau of Economic Research, Inc.
    2. Patrick Kline & Christopher R. Walters, 2016. "Evaluating Public Programs with Close Substitutes: The Case of HeadStart," The Quarterly Journal of Economics, Oxford University Press, vol. 131(4), pages 1795-1848.
    3. repec:wly:emetrp:v:85:y:2017:i::p:1373-1432 is not listed on IDEAS
    4. Atila Abdulkadiroğlu & Joshua D. Angrist & Yusuke Narita & Parag A. Pathak, 2017. "Research Design Meets Market Design: Using Centralized Assignment for Impact Evaluation," Econometrica, Econometric Society, vol. 85, pages 1373-1432, September.
    5. Huber, Martin & Wüthrich, Kaspar, 2017. "Evaluating local average and quantile treatment effects under endogeneity based on instruments: a review," FSES Working Papers 479, Faculty of Economics and Social Sciences, University of Freiburg/Fribourg Switzerland.

    More about this item


    randomized evaluation; local average treatment effect; bounds;

    JEL classification:

    • J64 - Labor and Demographic Economics - - Mobility, Unemployment, Vacancies, and Immigrant Workers - - - Unemployment: Models, Duration, Incidence, and Job Search
    • J68 - Labor and Demographic Economics - - Mobility, Unemployment, Vacancies, and Immigrant Workers - - - Public Policy
    • H44 - Public Economics - - Publicly Provided Goods - - - Publicly Provided Goods: Mixed Markets


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