Polycentrism or dispersion? An approach based on the New Urban Economics

There is no clear dividing line between polycentrism and dispersion in the spatial structure of cities. One of the methods used to assess the level of polycentrism in comparison with the dispersion of employment in an urban region has been to compare the changes in jobs inside and outside subcentres. If the proportion of employment in subcentres increases to a greater extent than the percentage of jobs located outside the CBD and the subcentres, then the city tends towards polycentrism, while if the opposite is true, it tends towards dispersion. The aim of this study is to consider polycentrism according to the New Urban Economics approaches. Using this approach, polycentrism must not only be measured by the employment concentrated in subcentres, but also by its impact on the location and density conditions of employment as a whole. The empirical evidence provided enables both methodologies to be compared for the total number of jobs in the Barcelona Metropolitan Region between 1986 and 2001. The results show that the polycentrism of the BMR has been accentuated by the identification of new subcentres and the maintenance —or even accentuation— of their effect on the location and density conditions of other employment.