From the New York Federal Reserve:
After rising for a decade, the U.S. homeownership rate peaked at 69 percent in the third quarter of 2006. Over the next two and a half years, as home prices fell in many parts of the country and the unemployment rate rose sharply, the homeownership rate declined by 1.7 percentage points. An important question is, how much more will this rate decline over the current economic downturn? To address this question, we propose the concept of the “homeownership gap” as a gauge of downward pressure on the homeownership rate. We define the homeownership gap as the difference between the “official” homeownership rate and a recomputed rate that excludes owners who are in a negative equity position, meaning that the value of their houses is less than their outstanding mortgage balance. Our estimate of this gap suggests that the official homeownership rate will likely experience significant downward pressure in the coming years.
(Follow the link for a link to the full paper).