Why Do Cities Matter? Local Growth and Aggregate Growth

We study how growth of cities determines the growth of nations. Using a spatial equilibrium model and data on 220 US metropolitan areas from 1964 to 2009, we first estimate the contribution of each U.S. city to national GDP growth. We show that the contribution of a city to aggregate growth can differ significantly from what one might naively infer from the growth of the city’s GDP. Despite some of the strongest rate of local growth, New York, San Francisco and San Jose were only responsible for a small fraction of U.S. growth in this period. By contrast, almost half of aggregate US growth was driven by growth of cities in the South. We then provide a normative analysis of potential growth. We show that the dispersion of the conditional average nominal wage across US cities doubled, indicating that worker productivity is increasingly different across cities. We calculate that this increased wage dispersion lowered aggregate U.S. GDP by 13.5%. Most of the loss was likely caused by increased constraints to housing supply in high productivity cities like New York, San Francisco and San Jose. Lowering regulatory constraints in these cities to the level of the median city would expand their work force and increase U.S. GDP by 9.5%. We conclude that the aggregate gains in output and welfare from spatial reallocation of labor are likely to be substantial in the U.S., and that a major impediment to a more efficient spatial allocation of labor are housing supply constraints. These constraints limit the number of US workers who have access to the most productive of American cities. In general equilibrium, this lowers income and welfare of all US workers.

Enrico Moretti and Chiang-Tai Hsieh

National Bureau of Economic Research Working Paper

May 2015

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