This paper develops a theoretical foundation for the notion of differential urbanization, in which groups of large, intermediate-sized, and small cities go through successive periods of fast and slow growth in a continuum of development that spans the evolution of urban systems in developed and less developed countries. A model depicting net migration patterns over time for major metropolitan, intermediate-sized, and small urban areas identifies six stages of differential urbanization. Data from three countries that span the development spectrum are used to test the accuracy of this model. A distinction between mainstream and substream migration flows provides an indicator of the concurrent concentration and deconcentration forces shaping urban systems. Counterurbanization represents the final phase in the first cycle of urban development, and is followed by a second cycle in which urbanization and spatial concentration dominate once again. At advanced levels of urbanization, the model can be used to characterize the degree of development within regions or subregions of a country. Also, precise definitions are suggested for the “clean break,” the end of urbanization, and the beginnings and ends of polarization reversal and counterurbanization.
Development spectrum
