What are Cities? Density, Efficiency and Social Reactors


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Rent is Too High? It’s the Nature of Urban Growth

Traffic is a downside of density. Image by thienzieyung.

City traffic is a downside of a high-density space. Image by thienzieyung.

Bettencourt demonstrates mathematically that the denser the city, the faster the growth.   He writes that cities resemble stars, which are “also driven by attractive forces and become denser with scale.”  Batty refers to this phenomena as “superlinear scaling,”

Cities can grow so large that their social networks, and actual energy networks, dissipate, making the city inefficient; crime and traffic become problems.  Or, cities with little spatial capacity may find rents increase too much for the city to remain viable socioeconomically.

As Dr. Michael Batty of the Centre for Advanced Spatial Analysis, University College, London explained in his editorial on Bettencourt’s work:
“The larger a city, the greater the benefits with respect to attributes such as income earned, but also the greater the costs with respect to social interactions such as crime… There are also gains in efficiency of infrastructure provision, because as cities get larger, they use less space per capita for utilities, transport routes, and residential living. These allometric laws are demonstrable for socioeconomic attributes such as income, the production of patents, financial services, and crime, all of which scale superlinearly with respect to population.”

By plugging known factors into Bettencourt’s equations, urban planners can more easily spot what variables are impacting the city.

So, what are cities? They’re social reactors, fueled by density.


Batty, M. A Theory of City Size. Science. (2013).

Bettencourt, L. The Origins of Scaling in Cities. Science. (2013)

Bettencourt, L. Supplementary Materials for The Origins of Scaling in Cities. Science. (2013)

Santa Fe Institute. Luis Bettencourt. (2013).  Accessed June 26, 2013.

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