Is city-making a science?

New Urban Network

The longest pieces in The New York Times Magazine are often the most illuminating. That was certainly true in the Dec. 19 issue — the magazine’s tenth annual presentation of “The Year in Ideas.”

In a fascinating article, Jonah Lehrer wrote about Geoffrey West, formerly a physicist at Stanford University Laboratory and Los Alamos National Laboratory, who in 2002 began turning his scientific mind to questions about cities.

What makes a city grow and thrive? Why do megalopolises arise? Why do some cities decline? West felt that in light of the galloping urbanization occurring throughout the world — the US is now considered “82 percent urbanized” — a better understanding of urban activity is essential.

With Luis Bettencourt, another theoretical physicist who had abandoned conventional physics, West started gathering information on “a dizzying array of variables, from the total amount of electrical wire in Frankfurt to the number of college graduates in Boise,” Lehrer recounts in the article, available here.

Says Lehrer:

After two years of analysis, West and Bettencourt discovered that all of these urban variables could be described by a few exquisitely simple equations. For example, if they know the population of a metropolitan area in a given country, they can estimate, with approximately 85 percent accuracy, its average income and the dimensions of its sewer system. These are the laws, they say, that automatically emerge whenever people “agglomerate,” cramming themselves into apartment buildings and subway cars. It doesn’t matter if the place is Manhattan or Manhattan, Kan.: the urban patterns remain the same.

That would suggest that any two American metropolitan areas with similar populations ought to have very similar average incomes. I decided to check West’s assertion by choosing a couple of US “Metropolitan Statistical Areas” and comparing them with the help of census figures.

Not all of 2010 census statistics are available yet, so I used figures from 2000 to compare metropolitan Denver — which at that time had a population of 2,157,756 — and metropolitan Pittsburgh, whose population was 2,431,087. According to West and Bettencourt’s theory, Pittsburgh, with an advantage of 12.7 percent in population, should be a little wealthier per capita than Denver.

The median household incomes, however, were actually the other way around, if the Census was accurate. Median household income in the Pittsburgh area was $35,908, while Denver’s figure was $39,910, or 11.1 percent higher.

That might be a fluke, of course. So I compared two smaller metro areas of almost identical population; Madison, Wisconsin, whose population in 2000 was 501,774, and Augusta-Richmond County, Georgia, South Carolina, home to 499,684 people. The census identified Madison’s median family income as $55,159 and Augusta’s as $44,491, or 24 percent less.

The general rule about population size and average income, as spelled out in Lehrer’s article, didn’t hold true, at least in those two comparisons. Perhaps other factors needed to be included, such as the geographical spread of the metro area, age of the city, the area’s racial composition, or variations between one region and another. Something must have been left out.

But let’s return to West and Bettencourt. According to Lehrer, they came to see the metropolis as an organism, defined by its infrastructure, much like an animal. One of the curious aspects of animals is that the bigger they are, the less they need to eat, compared to their own weight. An elephant is 10,000 times the size of a guinea pig, but needs only 1,000 times as much energy.

In Lehrer’s visualization of the metropolis as organism, “The boulevard was like a blood vessel, the back alley a capillary.” Says Lehrer:

This implied that the real purpose of cities, and the reason cities keep on growing, is their ability to create massive economies of scale, just as big animals do. After analyzing the first sets of city data — the physicists began with infrastructure and consumption statistics — they concluded that cities looked a lot like elephants. In city after city, the indicators of urban ‘metabolism,’ like the number of gas stations or the total surface area of roads, showed that when a city doubles in size, it requires an increase in resources of only 85 percent..

This straightforward observation has some surprising implications. It suggests, for instance, that modern cities are the real centers of sustainability.

Why this would be “surprising” is a mystery to me. In 2009, David Owen of The New Yorkerwrote an entire book, Green Metropolis, about the superiority of cities from the perspective of sustainability. Green Metropolis (a New Urban News review is available here) pointed out that city dwellers use electricity, water, petroleum, and other resources more sparingly than residents of the suburbs or the countryside. City dwellers inhabit smaller quarters, driver shorter distances (if they drive at all), and generally participate in the efficiencies of scale. This view of urban versus dispersed development is now so widely accepted that the environmental movement has swung around to favoring compact growth. Cities enable people to consume less per capita.

But of course energy efficiency is not the reason why people settle in cities. Lehrer presents West and Bettencourt’s view of the worth of cities this way:

… cities are valuable because they facilitate human interactions, as people crammed into a few square miles exchange ideas and start collaborations. “If you ask people why they move to the city, they always give the same reasons,” West says. “They’ve come to get a job or follow their friends or to be at the center of a scene. That’s why we pay the high rent.”

West and Bettencourt end up in the realm of Jane Jacobs, explaining the role that the coming together of people — especially in casual exchanges — plays in stimulating creativity and generating productivity. The physicists-turned-urban-scientists attempt to quantify urban interactions and their value:

According to the data, whenever a city doubles in size, every measure of economic activity, from construction spending to the amount of bank deposits, increases by approximately 15 percent per capita. It doesn’t matter how big the city is; the law remains the same. “This remarkable equation is why people move to the big city,” West says. “Because you can take the same person, and if you just move them to a city that’s twice as big, then all of a sudden they’ll do 15 percent more of everything that we can measure.” While Jacobs could only speculate on the value of our urban interactions, West insists that he has found a way to “scientifically confirm” her conjectures. “One of my favorite compliments is when people come up to me and say, ‘You have done what Jane Jacobs would have done, if only she could do mathematics,’ ” West says. “What the data clearly shows, and what she was clever enough to anticipate, is that when people come together, they become much more productive.”

I’d agree that casual exchanges often spark ideas. But a lot depends on whom you’re having the exchange with. Some individuals teach you something useful; others don’t. It’s been quite a while since I reread The Death and Life of Great American Cities, but my sense was that although Jacobs saw casual exchanges as important to neighborhood bonds, some of the exchanges that gave birth to economic productivity were more planned. Individuals from throughout the metropolis came together with other individuals who shared a common interest. They weren’t all from within just a few square miles.

Selectivity was crucial, or at least it seems crucial to me.  In the New York of Jacobs’ time, and still today, you want access to the right conversational and work partners, from among the millions of people in a metropolis, if you’re going to use those exchanges to further your own economic or intellectual pursuits. You can have plenty of casual exchanges in a small village, but it’s unlikely that they’ll spark a great enterprise. The pool has to be big if you’re going to have much of chance of finding exactly the right partners.

Once you do have a generous-sized pool, it’s useful to have within it physical environments that facilitate interaction. That may very well be a walking neighborhood sprinkled with cafes and other public or semi-public spots where people can easily meet.

Lehrer acknowledges that density has its downside:

… Of course, these interpersonal collisions — the human friction of a crowded space — can also feel unpleasant. We don’t always want to talk with strangers on the subway or jostle with people on the sidewalk. West admits that all successful cities are a little uncomfortable. He describes the purpose of urban planning as finding a way to minimize our distress while maximizing our interactions.

But in Jacobs’ Greenwich Village, Lehrer points out, short blocks, mixed-use zoning, and the density associated with brownstones “made it easier to cope with the strain of the metropolis.”

Unfortunately, development patterns have often veered a long way from what Jacobs recommended.

In recent decades, though, many of the fastest-growing cities in America, like Phoenix and Riverside, Calif., have given us a very different urban model. These places have traded away public spaces for affordable single-family homes, attracting working-class families who want their own white picket fences. West and Bettencourt point out, however, that cheap suburban comforts are associated with poor performance on a variety of urban metrics. Phoenix, for instance, has been characterized by below-average levels of income and innovation (as measured by the production of patents) for the last 40 years. “When you look at some of these fast-growing cities, they look like tumors on the landscape,” West says, with typical bombast. “They have these extreme levels of growth, but it’s not sustainable growth.”

Lehrer’s article contains some assertions that look shaky when scrutinized. My hunch is that even in a relatively lengthy Times Magazine piece,  Lehrer had to condense much of West and Bettencourt’s theorizing, leaving out significant parts of their reasoning. Nonetheless, it’s clear that the two physicists have come up with intriguing insights and conjectures — ideas that are relevant to the current struggle over how cities and metropolitan areas should grow. It would be worth hearing more from them — perhaps at a Congress for New Urbanism event.