Assessing the influence of participation on decision making

Participation processes (PPs) are often promoted as tools to improve public policymaking, yet their causal impact on policy decisions remains inconsistent. Existing research on policy impact has faced criticism for lacking methodological rigor, transparency, and comparability, impeding knowledge cumulation. This paper addresses these gaps by providing methodological guidance for assessing the causal impact of PPs on collective decisions in public policy and administration. Drawing on established theories of causality and (Bayesian) process tracing, we introduce a counterfactual approach that asks whether a decision would have occurred without the PP. We outline fundamental principles and practical steps for delineating, and operationalizing key concepts, assessing the strength of evidence, and addressing uncertainties. An exemplary application to the Berlin Climate Citizens’ Assembly reveals that only a small share of its proposals influenced policy decisions. The few impactful proposals support theories that deliberative mini-publics can drive policy change by encouraging policymakers, enriching policies, and breaking deadlocks. However, many proposals had no impact due to overlapping with existing or planned policies, exposing inefficiencies in mini-public design. Involving policymakers in mini-publics might enhance their impact on policy decisions but could compromise their independence.