[URBAN NOTE] "The Real Reason Cities Are Centers of Innovation"

[rfmcdonald]

Emily Badger's article at The Atlantic Cities has gotten wide coverage.

"We think there’s an underlying completely different way of thinking here, which is very different from the economist’s way of thinking," says [Wei] Pan, a doctoral candidate in computational social science in the MIT Media Laboratory's Human Dynamics Lab. Previous work by researchers at the Santa Fe Institute has proven the math behind the power of cities: As they grow in population, all kinds of positive outcomes like patents and GDP and innovation (and negative ones like STDs and crime) grow at an exponential factor of 1.1 to 1.3.

This means that all the benefits (and downsides) that come from cities don’t just grow linearly; they grow super-linearly [. . .]

As for why this happens, though, Pan pushes aside theories about the location of manufacturing or the specialty of trade. "It’s more fundamental than that," he says. "Cities are about people. It’s just that simple."

In a new paper published in Nature Communications, Pan and several colleagues argue that the underlying force that drives super-linear productivity in cities is the density with which we're able to form social ties. The larger your city, in other words, the more people (using this same super-linear scale) you’re likely to come into contact with.

"If you think about productivity, it’s all about ideas, information flows, how easily you can access ideas and opportunities," Pan says. "We believe that the interaction mechanism is what drives the productivity of the city."

It’s not possible for scientists to measure your social ties in the same way they can measure GPD or crime incidents or STD infections (despite their best wishes, they can’t put sensors on all of us). But this study examined a proxy for the same idea: The researchers looked at phone logs between anonymized telephone numbers all over the country, in search of the number of people who we communicate with inside our own metropolitan statistical area.

"If you look at the interaction patterns of cities," Pan says, "You will see that they grow super-linearly with population with the same growth rate as productivity, as innovation, as crime, as HIV, as STDs."

All of those facets of urban life have appeared until now to share a somewhat mysterious mathematical relationship. But this research suggests that this particular super-linear growth rate is directly tied to how dense cities enable us to connect to each other. As cities grow, our connections to each other grow by an exponential factor. And those connections are the root of productivity.

Of note is the fact that they suspect the productivity gains trail off when cities reach the 40 million mark, but since there are no cities that size as of yet it remains hypothetical.