Geographical distance puzzle in patent citations: intensive versus extensive margins

This paper explores the effects of geographical distance on knowledge spillovers through patent citations across 270 European regions. Despite decreasing transport and communication costs, geographical distance effects are strong and not decreasing. To address this distance puzzle, we distinguish between the extensive margin (the number of cited technologies) and the intensive margin (the average number of citations per technology) of patent citation flows. We confirm an increasing distance effect on knowledge flows at the extensive margin. We show it is compatible with decreasing transport and communication costs.