Another theory centers on an idea that the real estate market over the past few years "borrowed" buyers from the future to fuel the huge run up in housing prices.

"Homeowner rates increased more rapidly than they should have, and so that is why we say we 'borrowed' buyers from the future," says Chris Porter, manager with John Burns Real Estate Consulting. "We did that with low mortgage rates and loose lending standards. Now we are in a correction, moving back to more normal homeownership rates."

Anyone who might have been on the fence about buying over the past five years had the tools to make that purchase. Combine that with an ever-increasing housing supply coming from new home construction, and the record homeownership rates earlier in the decade just could sustain themselves.

"A study by the Federal Reserve Bank of Atlanta shows that most of this increase in homeownership was attributable to innovations in the mortgage market, rather than a demographic shift," Porter says. "The rise in the homeownership rate among the younger population in particular showed a greater acceleration."

In other words, people who may have waited to buy until, say, this year under normal conditions, actually bought their home in 2005 or 2006.

"This also means that the current pool of renters, as a whole, is less qualified to buy a home than usual, due to the fact that we already have drawn many of the more-qualified renters out of the rental pool," Porter says.

Yet a third factor driving up the number of renters in the market is the people who bought a new house before their previous home actually sold, says Lewis Goodkin, president of Miami-based real estate information firm Goodkin Consulting.

While they are stuck with two mortgages, the second house either sits vacant, driving down the homeowner numbers, or is rented to cover some of the costs rather than being sold at a loss -- which drives up the rental percentages.

"That is a function of people being not so eager to buy," says Mike Simonsen, CEO of Altos Research.

As the pool of potential buyers grows, they will slowly begin to replace those borrowed buyers, but with housing in a slump, those new potential buyers may not be in a hurry to jump into the housing market and the homeowner percentage may fall more before it rebounds.

Michael Giusti is a freelance writer and teaches journalism at Loyola University New Orleans.