Policy evaluation, randomized controlled trials, and external validity-A systematic review

•Systematic review of all RCT-based papers published in top economics journals.•The review assesses how these articles deal with external validity.•We find that the majority of papers does not discuss external validity issues.

This paper reviews all Randomized Controlled Trials (RCTs) published in leading economic journals between 2009 and 2014 with respect to how they deal with potential hazards to external validity: Hawthorne and John-Henry effects, general equilibrium effects, specific sample problems, and special care in treatment provision. We find that the majority of published RCTs does not discuss these hazards and many do not provide the necessary information to assess potential problems.

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