Derek Thompson and Jordan Weissmann writing in The Atlantic:
[T]he shift away from traditional suburbs toward denser, urban-light living could have major economic-growth implications on its own. Economic research shows that doubling a community’s population density tends to increase productivity by anywhere between 6 percent and 28 percent. Economists have found that more than half of the variation in output per worker across U.S. states can be explained by density. Our wealth, after all, is determined not only by our own skills and talents, but by our ability to access the ideas of those around us; there’s a lot to be gained by increasing the odds that smart people might bump against each other.