Source: http://www.washingtonpost.com/blogs/wonk...

Lighter areas contain newer construction, while darker areas are older. What stands out immediately is the difference between the Sunbelt--areas in the Southeast and Southwest where growth has been booming--and the Rustbelt--an arc stretching around the Great Lakes from North Dakota to New York. Nebraska and Kansas haven't seen much in the way of new construction either. This tracks pretty well with the overall population change in these areas. Over the past 10 years people have migrated to the Sunbelt and away from the Rustbelt.

Urban areas stand out as dark clusters of old housing stock surrounded by coronas of newer development.