A lot of this country is "built out" under current zoning regimes which require auto-oriented detached single-family construction in most of the country, which

A lot of this country is "built out" under current zoning regimes which require auto-oriented detached single-family construction in most of the country, which is extremely land-intensive compared to traditional walkable urbanism. Because land use in most of this country is very tightly regulated to prevent densification (or even cause de-densification in a lot of cities), most construction of new housing units has been on greenfield land at the outskirts of cities, so housing affordability has been correlated to access to new greenfield land at a city's edge, first via streetcar and street, then via expressway. As the interstate highway system has been completed, and all developable land within a reasonable driving distance of the most economically successful metro areas has been built on, people have instead been forced to bid up existing housing, hence the ridiculously high housing prices in most coastal metro areas and ongoing gentrification of central neighborhoods in these cities. Moreover, as time goes on, many people who've grown up in single-family-only, automobile-only neighborhoods have discovered they like walkable urbanism better, and the current zoning regime guarantees it is in short supply in many markets. Hopefully, we realize the economic folly of mandatory suburbanism as time goes on, and work to allow urbanization (a/k/a private property being used as its owners desire) in many mandatorily suburban areas now. It's happening to some degree already in Virginia: http://www.nytimes.com/2012/12/19/realestate/commercial/a-suburban-wasteland-in-virginia-gets-a-modern-urban-feel.html?pagewanted=all&_r=0 http://www.nytimes.com/2012/12/19/realestate/commercial/a-su... http://dc.streetsblog.org/2011/10/27/transforming-tysons-corner-a-high-stakes-suburban-retrofit/ http://dc.streetsblog.org/2011/10/27/transforming-tysons-cor...