Does the monocentric model work in a polycentric urban system? An examination of German metropolitan regions

In explaining the determinants of urban spatial structure, researchers have relied on the traditional monocentric ‘Alonso-Mills-Muth’ model. This article contributes to this discussion by testing the viability of the monocentric model when applied to metropolitan areas in Germany, a country traditionally associated with a polycentric urban structure, regional differences and urban shrinkage. We estimate the model with a unique dataset covering 92 metropolitan areas over two time periods (2000 and 2014), which allows estimation in both a cross-sectional and a panel framework. Using spatial and panel regression techniques, we test whether the underlying determinants of urbanisation vary according to factors unique to the German context, including the roles of historical geography, regional polycentricism and urban shrinkage. We found that, similar to the US studies, the model performed reasonably well, particularly with the overall fit and the performance of the population variable, which was significant and positively related to urbanised area. Personal income and land prices showed mixed results, and the coefficients for transportation costs proved to be challenging. We also found that regional geography matters: a region in eastern Germany is smaller than one in the west. A proxy variable for regional polycentricity was not significant. Finally, we found that the model’s behaviour differs between growing and shrinking regions, most notably in the differing impacts that population change has on the change in urbanised area.