Measuring the unmeasurable: the empirics of non-geographical proximity

This paper summarizes the empirical literature on the impact of non-geographical proximity on economic interactions. I identify two main criteria for classifying this literature: (i.) The way different types of non-geographical proximity influence different economic outcomes; (ii.) The recent turn of this literature from the simultaneous role of geographic and non-geographical proximity to empirical studies tackling the effect of pure non-geographical proximity. On the basis of these arguments, policy directions and directions for future research are discussed.