The first data set they analyzed was on the economic productivity of American cities, and it quickly became clear that their working hypothesis — like elephants, cities become more efficient as they get bigger — was profoundly incomplete. 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.

A Physicist Turns the City Into an Equation on NYTimes.com. A fascinating article about some constants between cities, and a bit at the end about how laws are different for corporations.