Some housing officials are worried that too many mortgage companies are lending to buyers who have no money to contribute to a downpayment and who ultimately will not be able to make the payments. They point to the growing popularity of adjustable-rate financing as another red flag.

While some economists have cautioned that housing prices have risen significantly more than economic fundamentals would appear to justify, creating the risk of a bubble, others state that the rising household incomes and low interest rates that have spurred home prices will keep the market from being thrown into any significant turmoil.

A new Federal Reserve report shows that American households owned $16.6 trillion in real estate during the third quarter of this year, an increase of 15.4 percent or $2.2 trillion from the same period a year ago.

The Office of Federal Housing Enterprise Oversight, meanwhile, reports that house prices have shot up 13 percent in the last 12 months and nearly 5 percent in just the third quarter, although such markets as Nevada and the District of Columbia have seen even bigger gains.