TRADE: Dr Greg Howard (University of Illinois Urbana-Champaign)

The Spatial Distribution of Population

Why do populations exhibit Zipf’s law nationally and within regions? This paper develops a model of location choice in which places substitute for one another at local, regional, and national scales. Heterogeneous geographic scope generates rank-size regularities and fractal spatial patterns. The model links bilateral migration flows to population cross-elasticities, yielding testable predictions: migration is nearly log-uniform in distance, follows gravity, and is disproportionately long-distance and large-city-to-large-city for bigger places. Observed migration flows discipline a quantitative cross-nested logit model. Combined with agglomeration, the model reproduces observed spatial distributions while reducing reliance on residual amenities.