The number of subcenters in large urban areas

We review and test Fujita and Ogawa's [Regional Science and Urban Economic 12 (1982) 161-196] model of urban spatial structure. The central theoretical prediction is that the number of employment subcenters rises with population and commuting costs. Simple Poisson regressions for a sample of 62 large American urban areas provide strong support for the theory, and these two variables alone account for nearly 80% of the variation in the number of subcenters. The results imply that an urban area with low congestion develops its first subcenter when its population reaches 2.68 million and its second subcenter at a population of 6.74 million.