Polycentricity and the evolution of metropolitan spatial structure

While evidence of polycentric urban form is extensive, questions remain regarding the value of agglomeration economies in an information economy, and hence whether polycentricity will persist over time. This paper examines employment spatial structure in four U.S. metropolitan areas between 1990 and 2009. We describe the spatial distribution of employment among centers and non-center locations across time, examine the persistence of center boundaries, and test for monocentric and polycentric form via density gradient estimations. Results show that the four areas are all polycentric but of different degree. Despite some small fluctuations, metropolitan spatial structure is persistent even in the face of economic shocks in the 2000s: employment centers have not lost their importance and influence in the metro-wide employment distribution over time.