The Size Distribution Across All "Cities": A Unifying Approach

Older cities in the US tend to be larger than younger ones. The distribution of city sizes is, therefore, systematically related to the country's city age distribution. We introduce endogenous city creation into a dynamic economic model of an urban system. All cities exhibit the same long-run growth rate (Gibrat's law), but young cities initially grow faster. The double Pareto lognormal (DPLN) emerges as the city size distribution in our model. The DPLN unifies the lognormal and the Pareto distribution (Zipf's law), and closely fits US city size data. This evidence can potentially resolve several debates from the recent literature.