The Spatial Variation of Urban Population Densities

OME years ago Colin Clark suggested that urban population densities beyond the limit of the central business district decline exponentially with distance from the center of the city.' Clark's work proved to be extraordinarily seminal. Others2 adopted his generalization as the law of spatial variation of urban population densities, and he himself published papers that elaborate on the concept.3 It now seems clear, however, that Clark's great contribution is principally in his exposition of the idea that urban population densities are in some way spatially systematic, rather than in the identification of a universally applicable model to describe the phenomenon; for the negative exponential formulation he proposed is actually only a good approximation of a more efficient, and a conceptually more relevant, model. In the present paper an alternative hypothesis of the spatial variation of urban population densities is proposed, which views the pattern of density within and beyond the limits of the central business district as a continuum, and which can be placed in a dynamic framework to provide for the emergence of a density crater in the central business district.