Pollution and city size: can cities be too small?

Abstract

We study optimal and equilibrium sizes of cities in a city system model with pollution. Pollution is a function of population size. If pollution is local or per-capita pollution increases with population, equilibrium cities are too large under symmetry; with asymmetric cities, the largest cities are too large and the smallest too small. When pollution is global and per-capita pollution declines with city size, cities may be too small under symmetry; with asymmetric cities, the largest cities are too small and the smallest too large if the marginal damage of pollution is large enough. We calibrate the model to US cities and find that the largest cities may be undersized by 3–4%.

Population density and urban air quality

“…Both of these papers use cross-sectional data. Borck and Tabuchi (2018) use panel data from US metropolitan areas. They find that per capita CO 2 emissions decrease with city size.…”

“…In this section, we present results from a simple urban economic model of city structure and pollution, building on Borck and Brueckner (2018), Borck and Pflüger (2015), Borck and Tabuchi (2018) and Larson and Yezer (2015). More details are in Appendix A.…”

Public transport and urban pollution

“…The larger β, the larger is the pollution damage. Borck and Tabuchi (2016) calibrate β in a similar model to match a social cost of carbon value of $40 per metric ton CO 2 which gives a value of β = 0.022. I use a slightly higher value of β = 0.05 here, but changes in β have only very small effects on the computed welfare effect.…”

Green cities? Urbanization, trade, and the environment

“…However, this literature is not conclusive on the sign of the effect. Oliveira, Andrade, and Makse () find increasing emissions, Gudipudi, Fluschnik, Ros, Walther, and Kropp () and Borck and Tabuchi () find decreasing emissions, while Fragkias, Lobo, Strumsky, and Seto () find that per capita emissions are essentially unrelated to population . In summary, the results vary between studies, with some finding increasing, others decreasing per capita pollution with an increasing population.…”

“…Further, we study more pollution sources, which makes our framework in principle useful for quantitative analysis of the relation between urbanization and pollution and for detailed policy analysis. Borck and Tabuchi () set up a model of a system of asymmetric monocentric cities with external increasing returns which assumes that there is a constant elasticity between a city's overall population and its overall emissions, whereas our model allows for an endogenously emerging relationship between city emissions and the economic activities within and between cities. Under their assumptions, in the case of global pollution, large cities may be too small in a free migration equilibrium if per capita pollution decreases with population and if the marginal damage of pollution is sufficiently large.…”