Why are cities such hubs of innovation and productivity? Consider the following from Triumph of the City by economist Edward Glaeser.Americans who live in metropolitan areas with more than a million residents are, on average, more than 50 percent more productive than Americans who live in smaller metropolitan areas.To further illustrate this phenomenon consider the following.In 2010**,* in the journal Nature, a pair of physicists at the Santa Fe Institute showed that when the population of a ...