Commenting on the concept of evidence-based policy, Jean Drèze argues that the relation between evidence and policy needs further thought. Based on his involvement with social policy in India, he believes that while economists can contribute to more informed policy discussions and public debates they ought to be cautious in offering advice on policy design.
Once upon a time, ‘evidence’ was widely confused with randomised controlled trials (RCTs). The latter were held to be the paragon of rigour, and other forms of evidence, though not necessarily dismissed, were certainly devalued. Whenever observation, experience, reasoning, or even statistical analysis suggested one thing and some RCT another, there was a tendency to assume that the RCT got it right. If not with evidence tout court, RCTs became synonymous with ‘rigorous evidence’ or ‘hard evidence’. The privileged status of RCTs was expressed in statements such as “all too often development policy is based on fads, and randomised evaluations could allow it to be based on evidence” (Duflo and Kremer 2005).
Today, the fever has come down and most economists would take a more nuanced view of what constitutes evidence. We also have a better understanding of the uses and misuses of RCTs. For this we owe a great deal to Angus Deaton and Nancy Cartwright, as well to many others who have contributed to the debate on both sides. Deaton and Cartwright (2018) present a particularly lucid and insightful assessment of the logic, power, and limits of RCTs.
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