Why innovation thrives in cities

Jun 04, 2013 by Larry Hardesty

In 2010, in the journal Nature, a pair of physicists at the Santa Fe Institute showed that when the population of a city doubles, economic productivity goes up by an average of 130 percent. Not only does total productivity increase with increased population, but so does per-capita productivity.

In the latest issue of Nature Communications, researchers from the MIT Media Laboratory's Human Dynamics Lab propose a for that "superlinear scaling": Increases in urban density give residents greater opportunity for face-to-face interaction.

The new paper builds on previous work by the same group, which showed that increasing employees' opportunities for face-to-face interaction could boost corporations' productivity.

In those studies, the researchers outfitted employees of a bank, of an IT consulting firm, and of several other organizations with tiny transmitters, developed by the Human Dynamics Lab, that actively measured the time the wearers spent in each other's presence. Obviously, that approach wouldn't work in a study of the entire populations of hundreds of cities.

So Wei Pan, a PhD student and first author on the new paper, looked at a host of factors that could be used to predict what the researchers are calling social-tie density, or the average number of people that each resident of a city will interact with in person. Those factors include things like the number of call partners with whom a will end up sharing a , instances of colocation with other users of location-tracking social-networking services like Foursquare, and the contagion rates of diseases passed only by intimate physical contact.

The availability of different types of data varied across the hundreds of cities in the United States and Europe that the researchers considered. But Pan and his colleagues concocted a single formula that assigned each city a social-tie-density score on the basis of whatever data was available. That score turned out to be a very good predictor of each city's productivity, as measured by both gross domestic product and patenting rates.

Planning for productivity

"When you pack people together, something special happens," says Alex "Sandy" Pentland, the Toshiba Professor of Media Arts and Science and director of the Laboratory. "This is the sort of thing that Adam Smith wanted to explain. He explained it through specialization: People were able to narrow what they did to get better at it, and because they were nearby, they could trade with each other. And Karl Marx described a different kind of specialization, which is classes—management class, owner class and proletariat. And other people have come up with other explanations for this basic phenomenon."

What the new work shows, Pentland says, is that "a lot of the things that people have been arguing about for centuries are not actually things that need explaining. They just come from the basic pattern of social networks."

The work could, however, have very real consequences for urban planning. For instance, Pentland says, there's evidence that the principle of superlinear scaling does not hold in poor countries, even in cities with the same population densities as major European and American cities. "The reason is that the transportation is so bad," Pentland says. "People might as well be in the village, because they only interact with their little local group."

Similarly, Pan says, "People know that when a city's population grows, there's scaling, and the productivity increases. But in these megacities, especially in China, no one knows whether that scaling will continue, because no other city is that big."

In Beijing today, Pan says, "it's really hard to move from one side to the other. I believe, personally, that social-tie density will drop because you can't really move freely anymore with the population increases. Unless Beijing solves these transportation problems, pumping in more people won't continue to drive the density."

Pentland adds that another figure that usually scales superlinearly with urban population is crime. But an exception to that rule is Zurich. "For various reason, its population has exploded in the last 20 years," Pentland says. "And they knew this was going to happen because of demographics. So they invested just an unholy amount of money in public transportation. You end up with this cloud of towns around Zurich, but everybody can get into Zurich in 15 minutes. More than 60 percent of the population moves into the center of Zurich during the day." As a consequence, Pentland says, Zurich enjoys all of the productivity benefits of social-tie density with much lower crime rates.

"In the next 10 years, we expect that India and China will each build a hundred cities of a million people or more," Pentland says. "Hopefully, what we can do is help them make better choices in designing these cities."

Explore further: Migration patterns reveal much about US population, research finds

Related Stories

Strong urban cores promote socializing in the city

Apr 15, 2013

Long commute times and urban areas that leapfrog over open space make it harder for people to socialize, but cities that are decentralized are even worse, University of Utah researchers say in a study published online today ...

Urban vegetation deters crime in Philadelphia

Mar 25, 2013

Contrary to convention, vegetation, when well-maintained, can lower the rates of certain types of crime, such as aggravated assault, robbery and burglary, in cities, according to a Temple University study, "Does vegetation ...

More move in than out of NYC: First time in decades

Mar 14, 2013

For the first time in more than 60 years, more people moved into New York City than out last year, a turnaround that tracks changing attitudes about the biggest city in the U.S. and urban living more broadly, officials and ...

Recommended for you

Study finds law dramatically curbing need for speed

Apr 18, 2014

Almost seven years have passed since Ontario's street-racing legislation hit the books and, according to one Western researcher, it has succeeded in putting the brakes on the number of convictions and, more importantly, injuries ...

Newlyweds, be careful what you wish for

Apr 17, 2014

A statistical analysis of the gift "fulfillments" at several hundred online wedding gift registries suggests that wedding guests are caught between a rock and a hard place when it comes to buying an appropriate gift for the ...

Can new understanding avert tragedy?

Apr 17, 2014

As a boy growing up in Syracuse, NY, Sol Hsiang ran an experiment for a school project testing whether plants grow better sprinkled with water vs orange juice. Today, 20 years later, he applies complex statistical ...

Creative activities outside work can improve job performance

Apr 16, 2014

Employees who pursue creative activities outside of work may find that these activities boost their performance on the job, according to a new study by San Francisco State University organizational psychologist Kevin Eschleman ...

User comments : 0

More news stories

Egypt archaeologists find ancient writer's tomb

Egypt's minister of antiquities says a team of Spanish archaeologists has discovered two tombs in the southern part of the country, one of them belonging to a writer and containing a trove of artifacts including reed pens ...

NASA's space station Robonaut finally getting legs

Robonaut, the first out-of-this-world humanoid, is finally getting its space legs. For three years, Robonaut has had to manage from the waist up. This new pair of legs means the experimental robot—now stuck ...