Does Evidence Affect Policy Making? A conjoint experiment among local government officials

While the importance of Evidence-Based Policy Making (EBPM) is widely recognized, actual policy formation is a complex process involving political and organizational coordination among diverse actors, and evidence does not necessarily affect real-world policy making. Using a conjoint experiment targeting local government officials, this study examines factors influencing policy choices and quantifies how different types of evidence affect decision-making. The results show that the existence of similar programs in neighboring municipalities strongly influences policy selection—in a comparable manner to the opinions of mayors, supervisors, and stakeholders. The study finds an asymmetry in the influence of evidence: while evidence indicating positive effects has a modest positive impact, evidence showing no effects has the strongest negative influence. Evidence from overseas cases exerts smaller effects than that from neighboring municipalities. Moreover, officials with statistical analysis experience and supportive attitudes toward EBPM rely more on rigorous evidence. These findings reveal both the realities and limitations of evidence use in policy processes and highlight challenges shared by evidence users and providers.