Abstract

Theories in regional science predict that related establishments benefit from their mutual proximity due to forward-backward linkages, labor market pooling and knowledge spillovers (the Marshallian forces). While the existence of these externalities as a whole is well supported by the empirical literature, there are few studies that discriminate between separate explanations. This paper introduces a new approach to assess the importance and magnitude of each of the Marshallian forces separately. Instead of measuring external economies of scale that take place within single industries, it models spillovers that happen between co-located industries. To this end, methods of spatial econometrics are adopted to measure interindustry relationships in employment growth between 55 industries of the manufacturing and service sectors in the labor market regions of the five largest cities in western Germany in the years 1989 to 2006. In this context, the strength of these relations is determined by economic closeness rather than by geography. The results suggest that each of the three Marshallian forces help to explain agglomeration externalities.