Ehrenhalt traces this demographic shift in terms of an "inversion." He discusses how Chicago's Sheffield neighborhood aptly serves as a model for this change. Long given up to drug dealers and gangs, Sheffield has diversified, reduced crime, improved schools, and raised property values all in a neighborhood, that as the author describes, is rather unremarkable in terms of architecture. He observes how people with choices prefer the walkable urbanism offered by Sheffield rather than the far-flung suburbs with their built-in commute time, isolation, and lack of sociability.
Ehrenhalt continues his inversion analysis across other cities: New York, Atlanta, Cleveland, Washington, Philadelphia, Houston, Phoenix, and Denver. His observations highlight, for example, how Phoenix's recognition of the need for a true "center city" finally led to its getting a grip on providing a real, urban alternative for young people who might want to stay in the state after graduating from college. He observes how, in Denver, developments in the Stapleton area and CityCenter Englewood can have mixed results when walkability and transit don't support walkable urbanism (p. 214-215). I'm surprised Ehrenhalt fails to discuss parking in any detail (for this, see The High Cost of Free Parking)-- because it is precisely in not getting parking right is where real, walkable urbanism breaks down. The boundaries between walkable streets to big box retail suffer when the obsession for free or underpriced parking literally squeezes out other uses. The people who are seeking real urbanism will be quickly turned off by acres of parking lots sucking the life out of a place.
Ehrenhalt fails most in that he does not explore more the limits and barriers on the great inversion he so aptly illustrates. He comes closest to doing this in the chapter on Philadelphia where he observes that the very tight grip of crime, decay, and abandoned post-urban land surrounding Center City Philadelphia retards the city's advancement. Indeed, Philadelphia's rich history, deep roots in American history, and stellar cultural and intellectual life, should place it as a "capital" city--of something--yet it falls short. Ehrenhalt points out that row-house property ownership and racial segregation play a role in hemming in Philadelphia. Ehrenthalt fails to comprehensively define, articulate, and call-out the many forces and players who do not want this "inversion" across all his cities. Indeed, Ehrenhalt's tone throughout the book is that this "inversion" is inevitable, unstoppable, unchallenged, and a consequence of inevitable demographic changes. But as he observes in Philadelphia--a constrained supply of safe, usable, walkable urban property diminishes the blossoming of city's fortunes. What are the forces that are behind these constraints? Who would be against a greater supply of usable urban land? Who would be against a bigger supply of affordable housing? Who would be against more diverse and better-performing inner city schools? Who would be against racial diversity in cities? What groups, organizations, and individuals might want to see the burbs remain as the ONLY choice for money and jobs? What groups would like to see the automobile as the ONLY choice for transportation? I think Ehrenhalt's book fails to address these questions, but it is an otherwise perceptive book about how demographics drive cultural geography.