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Researchers find ‘large is smart’ for cities

April 16, 2007

Cities are considered by many to be a blessing and a curse. Large cities generate considerable wealth, are home to many high-paying jobs and are known as engines of innovation. But cities also generate much pollution, crime and sometimes degraded social environments that lead to the urban blight that plague their very existence.

Now a team of researchers, including an economist from ASU, has studied the growth of cities in different parts of the world and has come up with general equations that can foretell their resource consumption patterns, as well as their contributions to society. The work has debunked the notion that cities act like biological organisms, in the sense that they grow to a finite size and consume resources in ways that decrease per capita with size.

“It’s true that large cities have more problems, they are more congested, they create more pollution and they have more crime,” says Jose Lobo, an ASU economist in the Global Institute of Sustainability and the School of Human Evolution & Social Change. “But also because of their size, cities are more innovative and create more wealth per capita. Large cities are the largely the source of their problems but they also are disproportionately the creators of the solutions to the problems of society at large.”

The researchers working with Lobo – Luis Bettencourt of Los Alamos National Laboratory, Los Alamos, N.M.; Dirk Helbing and Christian Kuhnert of Dresden University of Technology, Germany; and Geoffrey West of the Santa Fe Institute, Santa Fe, N.M. – detailed their findings in the article “Growth, innovation, scaling and the pace of life in cities,” in the current issue of the Proceedings of the National Academy of Sciences. An online version of the article was published April 16 at the Web site

“Humanity has just crossed a major landmark in its history with the majority of people now living in cities,” the researchers state. “The inexorable trend toward urbanization worldwide presents an urgent challenge for predictive, quantitative theory of urban organization and sustainable development.”

This will require thinking about cities in new ways.

The old way of thinking about cities is as if each one was an organism that consumes resources and grows in size. Oftentimes, cities are referred to as their own ecosystems, and many use the metaphor of them acting like biological organisms, Lobo says.

“The one thing that we know about organisms, whether it be elephants or sharks or frogs, is that as they get large, they slow down,” Lobo says. “They use less energy, they don’t move as fast. That is a very important point for biological scaling.

“In the case of cities, it is actually the opposite. As cities get larger, they create more wealth, and they are more innovative at a faster rate. There is no counterpart to that in biology.”

In fact, Lobo sys, the larger the city, the greater return on investment.

The researchers base their findings on data on the growth of cities (metropolitan areas) in the United States, Europe and China over the past 150 years. They analyzed cities consumption of resources (such as water or electricity usage), requirements for infrastructure (roads, transportation and lengths of electrical cable), and they also compiled and analyzed data on the creative output of these areas (patents issued, “super-creative jobs” generated, research and development employment, and total wages).

What they found were some general correlations of size and resource consumption that more or less fit the biological organism metaphor, meaning as the city grew in size it required less energy (resources) to sustain it in a proportion called sublinear scaling. What was surprising to the team was that the creative output (jobs, wealth generated and innovation), as cities grow, becomes faster and faster per capita.

“It isn’t like if you double the size of a city, you double its creative output,” Lobo said. “But it does increase by about 10 percent to 30 percent.

“We are not saying that any large city is assured of prosperity forever, but if you look at the collection of cities, large cities have managed to outrun their problems. Large is smart.”

All of this points to the need of rethinking large cities, both in how they are managed and what they contribute to the greater good. This is especially true today, as cities are on the brink of explosive growth in the developing world. Today, a little more than half of the world’s population lives in large urban areas. By 2030, it is estimated that two-thirds of the world’s population will be living in urban areas.

“Cities are really one of the most important innovations in human history,” Lobo says. “We need to think of them as being very human entities, and as engines of our collective creation. We need a different perspective about cities, one that is away from thinking of large cities as a source of problems, but rather as the possible and unavoidable sources of solutions.

“The practical application of this work is that the problem is not large cities. The problem is the conditions in which some of the people live in large cities. Policies should be directed to making large cities more livable, not making them smaller.”