Brown growth, green growth, and the efficiency of urbanization

We analyze the efficiency of urbanization patterns in a stylized dynamic model of urban growth with three sectors of production. Pollution, as a force that discourages agglomeration, is caused by domestic production. We show that cities are too large and too few in number in uncoordinated equilibrium if economic growth implies increasing pollution (brown growth'). If, however, production becomes cleaner over time (green growth') the equilibrium urbanization path reaches the efficient urbanization path after finite time without need of a coordinating mechanism. We also generalize these results by taking other forms of congestion and urban land markets into account.