Does Policy Diffusion Need Space? Spatializing the Dynamics of Policy Diffusion

For decades, scholars in multiple disciplines have examined spatial diffusion, or the spatiotemporal properties associated with the diffusion of innovations. These properties include contagious, hierarchical, and relocation diffusion. Each of these refers to a spatial model that epitomizes how innovations spread among geographic locations. Policy diffusion, a separate but homologous research tradition, had its theoretical underpinnings in spatial diffusion. However, contemporary policy diffusion has focused largely on mechanism-based diffusion. This article demonstrates how exploratory spatial data analysis can be used to uncover spatial policy diffusion properties. In this study, municipal smoking regulation adoptions, religious-based initiatives, and bag ban and bag fees are examined. This study finds evidence that for each policy more than one property is occurring; therefore, this study proposes that a hybrid model best explains diffusion. This article demonstrates how examining spatial diffusion properties, in addition to diffusion mechanisms, can improve the conceptualization of diffusion theories, enhance mechanism or theory-based specification of diffusion models, and unravel the specific regional or neighboring causal pathways linking policies between adopting jurisdictions.