The Diffusion of Exclusion: Medieval Expulsions of Jews

What social processes guide the spread of ethnic or racial exclusion? I investigate the diffusion of medieval expulsions of Jews among over 500 polities in the western Holy Roman Empire, 1385-1520 CE. For medieval governors, religious and material concerns were strong rationales against expulsion. Yet expulsions increase markedly in the 15th century. Did an expulsion by one government affect another government's choices about expulsion? I appraise three common theories of policy diffusion: learning, social reinterpretation, and social structural and resource constraints. Statistical models provide evidence only for the latter two. While theological changes gave expulsion fresh political value, the adoption of expulsion followed political and economic incentives that were embedded in inter-city relationships of power and dependency. The results indicate that social influence, especially spatial proximity, cannot be assumed to accelerate ethnoracial extremism.