Gruber explains how "cultural bias against the city" had an effect:
"In Europe during the same period of economic and technological change cities largely retained their primacy for the middle and upper classes, while the suburbs became the home of the working-class and poor. In the U.S., the single-family house in a faux rural setting became the norm for the middle-class, and even in metropolitan areas that remained relatively prosperous the middle-class largely abandoned central cities. To say that suburban sprawl happened because of favorable governmental policies only begs the question why those were the policies. Did they reflect a bias against cities, rooted in Jeffersonian rural populism?"
Gruber notes the impact of automobiles, but points out that other nations have managed to incorporate cars without destroying their urban centers. He also considers the impact of immigration and racism, and the ideological shift that came from modernism.