The structure of sprawl - Identifying and characterizing employment centers in polycentric metropolitan areas

This paper applies a consistent framework to four comparably sized metropol itan areas to identify and characterize their employment centers. Employmen t centers are identified as places that exceed a threshold employment densi ty and a threshold employment level, They are also characterized as special izing on the basis of location quotient analysis. We find clear evidence of specialization in every employment center in the four metropolitan areas s tudied. Our interpretation is that what we are observing is a systematic ch ange in metropolitan structure rather than a random sprawling of firms, We also find some evidence that the size distribution of employment centers fo llows the rank-size rule, This suggests that there is structure not only in the distribution of economic activity among the employment centers but als o in their size distribution. Because less than 50 percent of metropolitan employment is within employment centers, future research should focus on un derstanding the more diffuse employment patterns, The rank-size rule gives some guidance as to the expected size distribution of employment throughout the metropolitan area.