Can Politicians Discriminate Between Good and Bad Evidence? Experimental Results from 3,500 European Politicians

How do politicians evaluate and respond to evidence? Organizations and political authorities across the world invest significant resources to provide evidence to the policy-making process. However, the ability of policymakers to use this evidence remains an open question. In three experiments with 3,500 mayors and councillors from six Western democracies, we find only basic levels of statistical literacy. Representatives treat convenience samples, imprecise estimates, and correlational evidence as less informative. However, baseline levels of statistical literacy are low and a majority of local politicians treat unreliable evidence as informative. Moreover, statistical literacy does not necessarily translate into persuasion. In the presence of large effect sizes, officials are equally persuaded by high- or low-quality evidence. More professionalized politicians are no better equipped to evaluate evidence. The results uncover concrete obstacles for politicians to incorporate evidence in policy-making and identify steps to overcome these obstacles.