@TechReport{iza:izadps:dp18453, author={Grewenig, Elisabeth and Gruendler, Klaus and Lergetporer, Philipp and Potrafke, Niklas and Werner, Katharina and Zeidler, Helen}, title={Expertise and Prediction Accuracy}, year={2026}, month={Mar}, institution={Institute of Labor Economics (IZA)}, address={Bonn}, type={IZA Discussion Paper}, number={18453}, url={https://www.iza.org/publications/dp18453}, abstract={Public support for policy interventions depends on citizens’ beliefs about their likely effects. We examine how individuals form such beliefs by studying their predictions of experimental outcomes in a policy-relevant setting, and why their predictions differ from expert benchmarks. We elicit forecasts from 127 professional economists and a representative sample of 6,200 German households about a large-scale behavioral experiment on education policy (N = 3, 133). Nonexperts predict both average outcomes and treatment effects far less accurately than experts. Prediction accuracy improves with calibrated priors, self-reported effort, and the use of structured reasoning, but remains well below expert levels. We show that scalable design features, including the provision of well-calibrated numerical anchors and monetary incentives to rise effort, improve non-expert predictions, with effects comparable in magnitude to tertiary education or structured reasoning. Our findings have important implications for bridging the ‘expertise gap’ in public discourse.}, keywords={expert forecasts;lay predictions;belief formation;expertise gap;policy support;behavioral experiments}, }