Americans, especially generations X and Y, want shorter commutes, walkability and a car-free existence. Which means that around 40 million large-lot exurban McMansions, built primarily during the housing boom, might never find occupants.

Only 43 percent of Americans prefer big suburban homes, says Chris Nelson, head of the Metropolitan Research Center at the University of Utah. That mean demand for “large-lot” homes is currently 40 million short of the available stock — and not only that, but the U.S. is short 10 million attached homes and 30 million small homes, which are what people really want.

“If we are optimistic that the world is not coming to an end and we’re going to get out of this economic trough, it’s a good time to consider, when production does ramp up, how we will be building as a country,” [says Joe Molinaro head of the National Association of Realtors' smart growth program.]