“The rate [of home ownership] only began to climb above 64 percent in the 1990s and the first decade of the current century when Administrations of both parties adopted national policies designed to encourage home ownership; the result was to drive both home prices and the home ownership rates to unsustainable levels”.–”Housing in America: The Next Decade,” Urban Land Institute

The percentage of those in the U.S. that are homeowners has fluctuated throughout U.S. history. As mentioned in the quote, the home ownership rate peaked in 2004 at 69%.
Here is the U.S. homeownership breakdown as provided by the Urban Land Institute (ULI):
- 1900-1930: 45% to 48%
- 1940: 43% (The reduced amount was due to the Depression and World War II.)
- 1945-1960: 62% (This was the period of “the great suburbanization of the U.S.” The factors leading to this suburbanization was “a booming economy, rising real incomes, favorable tax laws, a rejuvenated home building industry, and easier financing.“)
- 1960-1990: 62% to 64%
- 2004: 69%
- First quarter 2009: 67.2%
- Likely near-term stabilization rate: 62% to 64%
ULI provides the following analysis on the effects that a change in the number of homeowners will have in the U.S.:
“Government policies are in the process of being rebalanced today. A homeownership rate of 62 to 64 percent will have only a modest impact on local communities….
There have been many studies which extol the virtues of homeownership for community stability and educational and health benefits for children. These are being questioned by new studies, however, and new evidence suggests that housing stability is more important than whether a home is owned or rented in producing positive outcomes.
If, on the other hand, a confluence of circumstances conspires to produce a rate in the 50s, this will be a “game changer.” The most likely cause for such a low homeownership rate would be a prolonged or double dip recession, with a slow recovery”.–Urban Land Institute
To see a ULI video presentation of the report, click here. To read the ULI report, click here. To read a related report from ULI, see “2010 Emerging Trends in Real Estate“