Empirical Polycentricity: The Complex Relationship between Employment Centers

This paper empirically finds that employment subcenters have the expected connections with the central business district, but additionally have important relationships with each other. Using data from Houston, Texas, USA, we use a new proximity measure to estimate a polycentric density function, and show that the estimated gradient using the total derivative, allowing for the relationship between all subcenters, is much different than the gradient using only the own center coefficients. Further, we model asymmetry in the density function by limiting the employment center influence using commuting data, and testing the influence of over-lapping areas for both population and employment. We find significant asymmetry both within, and even outside of the commuting areas. We conclude that subcenters have important linkages to each other in addition to the CBD, and that therefore the polycentric city is more complex than additional centers mimicking the CBD.