Three essays on spatial frictions[Trois essais sur les frictions spatiales]

Spatial frictions are key to explain many economic phenomena. This thesis provides three pieces of evidence on the origins, prevalence and consequences of such frictions.In the first chapter, we focus on spatial frictions in the diffusion of knowledge. We explain the puzzling persistence and stability of the spatial decay in patent citation flows by innovator networks. We establish that knowledge percolates: firms disproportionately cite new patents from prior contacts, and form links with contacts of their contacts. Embedding this percolation into a network formation model is sufficient to rationalize the negative link between aggregate knowledge flows and distance.In the second chapter, we shed some light on the role of spatial information frictions in shaping international trade flows. We use the specific context of the XIXth Century, during which the creation of international news agencies facilitated the transmission of information across countries. We show that trade between a pair of countries increases when both are covered by a news agency. The reduction in information friction was therefore one of the many factors behind the First Globalization.The last chapter investigates whether transport costs are the main component of within-country trade costs. While it is well-established that international trade costs are not limited to transport costs, evidence is much scarcer for intra-national trade flows. We use hurricane Sandy as a natural experiment shifting upwards transport costs in some areas of the US to establish that if transport costs were the sole driver of the distance elasticity of trade flows within the US, this distance elasticity would be much lower.