Innovation

The urban ability to create collaborative brilliance isn't new.  For centuries, innovations have spread from person to person across crowded city streets.  An explosion of artistic genius during the Florentine Renaissance began when Brunelleschi figured out the geometry of linear perspective.  He passed his knowledge to his friend Donatello, who imported linear perspective in low-relief sculpture.  Their friend Masaccio then brought the innovation into painting.  The artistic innovations of Florence were glorious side effects of urban concentration; that city's wealth came from more prosaic pursuits:  banking and cloth making.  Today, however, Bangalore and New York and London all depend on their ability to innovate.  The spread of knowledge from engineer to engineer, from designer to designer, from trader to trader is the same as the flight of ideas from painter to painter, and urban density has long been at the heart of that process. 

The vitality of New York and Bangalore doesn't mean that all cities will succeed.  In 1950, Detroit was America's fifth-largest city and had 1.85 million people.  In 2008, it had 777 thousand people, less than half its former size, and was continuing to lose population steadily.  Eight of the ten largest American cities in 1950 have lost at least a fifth of their population since then.  The failure of Detroit and so many other industrial towns doesn't reflect any weakness of cities as a whole, but rather the sterility of those cities that lost touch with the essential ingredients of urban reinvention. 

Cities thrive when they have many small firms and skilled citizens.  Detroit was once a buzzing beehive of small-scale interconnected inventors--Henry Ford was just one among many gifted entrepreneurs.  But the extravagant success of Ford's big idea destroyed that older, innovative city.  Detroit's twentieth-century growth brought hundreds of thousands of less-well-educated workers to vast factories, which became fortresses apart from the city and the world.  While industrial diversity, entrepreneurship, and education lead to innovation, the Detroit model led to urban decline.  The age of the industrial city is over, at least in the West.

Edward Glaeser,

Triumph of the City, pp.8-9