According to the 2007 AHS, monthly housing costs accounted for 30% of a median renter household's monthly income, versus about 20% for homeowners. It's important to note, however, that about a third of owners own their homes free and clear, with no mortgage or equity debt, so that may skew the AHS final figures a bit. Moody calculates that housing costs take up some 28% of monthly income for homeowners with mortgage debt--still lower than for renter households.

Similarly, the Harvard University's Joint Center for Housing Studies defines a moderate housing cost burden as one spending 30% to 49% of monthly household income on housing costs, and a severe cost burden those spending 50% or more. By that definition, there are a great deal more renters also carrying a larger burden of housing costs. As of the 2007 AHS, 50.66% of all renter households carry a moderate--31.47%--or severe--19.19%--housing cost burden, which of course is more severe when the household in question is low income.

These findings have great implications for rental housing owners and policymakers. With lower-income households more likely to be hurt by the job losses in the past and coming years, it's more likely that those households would double up with roommates or move back in with family.

At the same time, the fallout in the for-sale residential market is helping to push demand for rentals, be it by former homeowners who have been foreclosed upon, or those unable to obtain a mortgage in today's tighter climate. But even those households would have limited room to maneuver when it comes to being able to pay more for housing. "This would suggest that rental property owners will have to be more discerning in seeking to push rent increases at a time when tenant retention is critical," says Moody.

Meanwhile, the renters by choice--that is, those who are unwilling to make the leap into the uncertain homeownership pool--would be less likely to be burdened by rental housing costs. For these households, "there are considerably more options on the supply side of the market," and, therefore, would be more likely to rent a single-family home or luxury condo that's been put in the rental pool, rather than a traditional apartment, Moody explains.

"Thus, while the overall demand for rental housing continues to expand, the mix between necessity renters more likely to be cost burdened and renters by choice who are less likely so, is ever changing," says Moody. "Given the disparate forces at play, it could be the case that while a significantly higher share of lower income renter households will be contending with either a moderate or severe housing cost burden, these numbers could be offset--partially or fully--by a rising number of higher income renter households reporting no cost burdens."

So while the numbers may not show a significant difference, individual property owners and managers are likely to notice these shifts. Add to that the growing numbers of younger renters entering the workforce and immigrants, as well as the tighter mortgage lending conditions, and Moody says the demographics of rental households will continue to change over the next several years.

"It seems clear that, even aside from near-term cyclical factors, the longer-term trend is for greater shares of lower and middle income renter households to face increasing housing cost burdens," says Moody.

"Clearly, there is ample room for a policy response, particularly one not tied to the notion that constantly expanding homeownership is the be all and end all of housing policy," he adds. "For instance, a greater emphasis on development of workforce housing--for those earning between 60% and 120% of area median income--would fill a void now being left by the market, and one that threatens to widen over coming years."