My main problem with RCTs is that they make us think about interventions, policies, and organizations in the wrong way. As opposed to the two or three designs that get tested slowly by RCTs (like putting tablets or flipcharts in schools), most social interventions have millions of design possibilities and outcomes depend on complex combinations between them. This leads to what the complexity scientist Stuart Kauffman calls a “rugged fitness landscape.”

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RCTs may be appropriate for clinical drug trials. But for a remarkably broad array of policy areas, the RCT movement has had an impact equivalent to putting auditors in charge of the R&D department. That is the wrong way to design things that work. Only by creating organizations that learn how to learn, as so-called lean manufacturing has done for industry, can we accelerate progress.

The Problem With Evidence-Based Policies
https://www.project-syndicate.org/commentary/evidence-based-policy-problems-by-ricardo-hausmann-2016-02