“…This is in contrast to the spatial production function work of Druska and Horrace (2004) or Glass et al (2014), where the unit of observation is the firm, and exogenous networks are conceptualized as output/input spillovers across firms (or countries) measured as geographic distances or contiguity in a spatial estimation framework, and where consistency arguments are for large numbers of firms (or countries). In these papers it is not easy to conceptualize the network (spillover) mechanism or to argue that the adjacency matrix is the correct 11 There is a large literature that exploits random allocation of individuals into groups to assess the existence of peer effects in other (non-productivity) contexts (e.g., Sacerdote, 2001;Angrist and Lang, 2004;Kling et al, 2007;Chetty et al, 2011;Duflo et al, 2011;Carrell et al, 2013).…”