Scientists predict characteristics of cities

December 1, 2010—Cities are some of the most complex human organizations, yet they share remarkably similar characteristics as they grow in size. The developed world is already about 80% urban, and the rest of the world is expected to follow suit by 2050. Urbanization defines much of what we can expect to experience in our homes, work, and social interactions.

Luis Bettencourt of the Lab's Applied Mathematics and Plasma Physics/Center for Nonlinear Science groups and the Santa Fe Institute and collaborators are developing a quantitative understanding of cities and the increasingly critical role they play in human societies and the sustainability of the planet.

Toward a unified theory of sustainability

Bettencourt studies the structure and dynamics of complex systems, with an emphasis on dynamical problems in biology and society. He and his collaborators are working toward a unified theory of sustainability with cities and urbanization at its core — a predictive framework that can be applied to all cities worldwide. The issues associated with urban growth and global sustainability typically have been treated in isolation, but these issues are strongly interrelated. Without an understanding of the complexity and interrelatedness of cities, policy relating to cities and socio-economic development can be ineffective and sometimes disastrous.

The scientists found that size is the major determinant of most characteristics of a city, while history, geography, and design have secondary roles. General trends with increasing population can be expressed as a 15% "rule" - doubling a city's population requires only an 85% increase in infrastructure. On average, as city size increases, per capita wages and other socio-economic markers increase by 15% more than the expected linear growth. However, the same is true for negative markers such as crime, traffic congestion, and disease. Cities also display stability - successful city performance is sustained for several decades or longer, and cities suffering from urban decay can expect a long uphill battle to effect positive changes. The researchers developed scale-adjusted metropolitan indicators that allowed them to compare the socioeconomic performance of large, midsized, and smaller U.S. cities.

Knowledge is power

The more we learn about what makes cities tick, and what makes for successful urban growth, the better we will be able to understand and manage the socioeconomic potential of our nation and of an urbanized world. Collaborators include Geoffrey West of Santa Fe Institute and retired LANL Senior Fellow, José Lobo of Arizona State University, and Deborah Strumsky of University of North Carolina-Charlotte. Laboratory Research and Development (LDRD), the National Science Foundation, and the J.S. McDowell Foundation supported Bettencourt's work. PLoS ONE (Public Library of Science) published the research, which Nature featured in a special issue on "Building the Best Cities for Science".