Owning a home has long been seen as a pillar of the American dream. But a new report highlights just how far many Americans remain from achieving it.

Middle-income households, or those with annual earnings of up to $75,000, can afford only 23% of the homes listed for sale in the U.S., according to recent data from the National Association of Realtors (NAR). In a more balanced market, almost half of listings should be affordable to buyers of average income, the group said.

In fact, the housing market has a deficit of about 320,000 affordable homes, NAR found, which for moderate-income families ranges up to about $256,000. The median price for all homes is $388,000.

"Ongoing high housing costs and the scarcity of available homes continues to present budget challenges for many prospective buyers," Realtor.com Chief Economist Danielle Hale said in a report. "And it's likely keeping some buyers in the rental market or on the sidelines and delaying their purchase until conditions improve."

To be sure, many Americans of modest means are still finding ways to buy a home. Even for people below the national median household income of roughly $75,000, the rate of homeownership rate now tops 53%, according to Census data — a record high dating back to 1994, when the agency first started tracking the data. 

Still, a shortage of affordable homes isn't only an inconvenience — it's a major obstacle to building wealth.

"Put simply, there are currently more than 1 million homes available for sale," NAR said in the report. "If these homes were dispersed in a more adequate match for the distribution of households by income level, the market would better serve all households."

Some parts of the U.S. have a richer supply of mid-tier homes, according to the group's findings. Most of these locations are in the Midwest, where households that make under $75,000 a year generally have an abundance of properties to choose from. Three Ohio cities — Youngstown, Akron and Toledo — have the greatest number of affordable homes.

On the other end of the spectrum, El Paso, Texas; Boise, Idaho; and Spokane, Wash., have the fewest homes for middle-income buyers, according to NAR. And while it's generally known that real estate is beyond the means of most residents in expensive cities like New York and San Francisco, moderate-priced housing is also in short supply in southern states such as Florida and Texas typically thought of as more affordable for prospective homebuyers. 

In:
• Home Prices

Sanvi Bangalore

Sanvi Bangalore is a business reporting intern for CBS MoneyWatch. She attends American University in Washington, D.C., and is studying business administration and journalism.

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