WASHINGTON — Housing prices are far outstripping salary increases for low- and moderate-income jobs, putting the American dream of owning a home beyond the reach of teachers, firefighters and other community workers in many cities, said a study being released today.

The report, by a coalition advocating affordable housing, found that even cities once considered affordable, such as Tulsa, Okla., are rapidly becoming too pricey for lower-income workers such as janitors and retail sales employees.

The study found the median price of a home in the U.S. rose 20 percent in just 18 months, to $225,000. During the same period, wages for teachers, firefighters and nurses in most cities remained flat or increased slightly, but still fell far short of the annual salary needed to buy a home, the report from the Center for Housing Policy said.

For example, the median household income for a nurse rose 10 percent from 2003 to 2005, to about $36,000. For a firefighter, wages were flat, remaining at about $37,000 a year.

Those salaries don't come close to the $71,000 annual income needed to qualify to purchase a $225,000 home. The number is based on a down payment of 10 percent.

"It's not just the level of housing prices versus wages, but the fact that, especially in some areas, the housing prices are growing so much faster," said Barbara Lipman, research director for the center.

"It's creating this dynamic where people who work these jobs must feel like they'll never catch up. The dream of home ownership may be unattainable," she said.

It's a problem faced by many people in Hawai'i, where home prices have skyrocketed in recent years. On O'ahu, the median price for single-family homes in July was $599,000, up 25 percent from $480,000 a year ago and just shy of the record $610,000 set in May.

The study looked at incomes for more than 60 occupations, from janitors to accountants. It examined housing prices for nearly 200 metropolitan areas from the fourth quarter of 2003 to the first quarter of this year.

The least-affordable places in the country were the usual suspects: San Francisco, Orange County, Calif., and Northeast cities such as New York and Boston.

Some of the most affordable places were in the Midwest, places like Waterloo, Iowa; Saginaw, Mich.; and Lima and Youngstown, Ohio.

But Lipman said cities like Tulsa and Minneapolis, which had traditionally been thought of as more affordable, are now a concern.

"We're seeing a problem in areas where you'd expect and then beyond that because of the flatness of the wage growth and the increased pressures on home prices and rents," said Lipman. "Even though we have historically low interest rates, that doesn't solve the problem."

The study identified West Palm Beach, Fla., as one of the areas where there's a growing disparity between housing costs and sluggish wages for low- and moderate-income families.

The median home price in the Florida city has jumped nearly 32 percent since 2003, to $245,000. To qualify for a mortgage, a person would need to make about $77,600 a year, up from $57,600 in 2003. That would put a home out of reach for schoolteachers and police officers in the community, whose annual salaries are in the low to mid 40s.

The gap is even greater for nurses, who make about $36,000, and childcare workers, whose salaries are in the low to mid 20s.

The Center for Housing Policy is the nonprofit research affiliate of the National Housing Conference, based in Washington.