The city size distribution debate: Resolution for US urban regions and megalopolitan areas

Four phases of interest in the distribution of city sizes are identified and current conflict in the literature is shown to be a consequence of poorly-selected units of observation. When urban regions are properly defined, US urban growth obeys Gibrat's Law and the city size distribution is strictly Zipfian rank-size with coefficient q=1.0. Care has to be taken with definition of the largest urban-economic regions, however; the fit in the upper tail of the distribution is best when they are recognized to be megalopolitan in scale.