Politicians and Evidence

How do politicians evaluate and respond to evidence? Organizations across the world invest significant resources to produce policy evidence. Yet, politicians’ ability to use this evidence to inform policy decisions remains underexplored. In three experiments involving 3,521 mayors and councilors from six Western democracies, we find that representatives treat convenience samples, imprecise estimates, and correlational evidence as less informative. However, baseline levels of statistical literacy are low, and effect sizes are small. Compared to a sample of public policy experts, local politicians’ ability to discount unreliable evidence is 4-5 times lower. Moreover, statistical literacy does not necessarily translate into persuasion. When presented with large effect sizes, officials disregard the soundness of the evidence. More professionalized politicians are not better able to evaluate evidence. The results show that the prospects of informing policy with evidence will remain constrained without well-equipped decision-makers.