Rethinking “Distance from”: The Examples of Wittenberg and Mainz

An influential economic history literature uses distance-based variables as proxies for exposure, or access, to historical “treatment interventions” with potential economic impacts. This paper examines the assumptions underlying this practice and find s historical and econometric problems that engender misleading conclusions. Historical evidence challenges the assumption that physical proximity determined access to ideas or technology even in pre-industrial settings. Replication exercises and statistical simulations reveal that “distance from” variables frequently produce falsely significant estimates in first-stage instrumental variable (IV) and Ordinary Least Squares (OLS) regressions, and potentially violate the exclusion restriction in the IV second stage. My findings suggest caution in using distance-based measures as proxies for the diffusion of information and resources.