Society: Outstanding, Superlinear Cities

Bigger cities are more intense by nature: richer, more productive, more creative and more dangerous. Indeed, Bettencourt and his colleagues have shown, doubling the population of a city gives a 15 percent premium on each of these factors. Since New York City is the most populous city in the United States, New Yorkers should make more money, for example, than other Americans on average. To be exceptional, New Yorkers would need to be raking in even more than the princely sums you'd expect.

Turns out they're not. In an article this month in PLoS ONE, Bettencourt and his team created a way to measure how exceptional cities are by comparing their characteristics with what mathematics would predict for their size. The team then ranked the exceptionality of 300 U.S. cities based on personal incomes, gross metropolitan product (GMP), number of patents and number of violent crimes. On income, the New York metropolitan area came out a measly 85th place, just 3.8 percent above what one would predict for its size. On GMP, it ranked 167th, and on patents, it ranked 178th. The only exceptional number was for crime, which was surprisingly low: 267th out of 300, a whopping 22 percent below the typical rate for its size.

San Francisco, on the other hand, is rich, productive, creative and moderately safe for its size. By the team's rankings, the San Francisco metropolitan area comes out 12th for personal income, 19th for patents, 27th for GMP and 131st for violent crime.

To identify what's special about a place, you have to separate out the factors that are really just about its size, Bettencourt says. Then you can disentangle the general effects of urbanization from the specific character of a town.

Ideas, the team believes, are the real driver of economic activity and creativity, and when people are in closer contact — as they are in big cities — they tend to share those ideas more. A magazine designer in New York, for example, is much more likely than one in Huntsville, Ala., to bump into someone who knows about new design software or a clever layout trick. As a result, twice as many people are more than twice as productive — a phenomenon known as superlinear scaling, since the increase is faster than a linear equation would predict. That's the origin of the 15 percent premium on per capita income, patents and GMP that Bettencourt and his colleagues have documented in cities around the world. Similarly, crime increases superlinearly as people share bad ideas.

For more, see Outstanding, Superlinear Cities by Julie Rehmeyer, December 6, 2010 at ScienceNews.