There simply aren't enough rental homes available to extremely low-income households in Illinois, according to a new report, and housing advocates say that needs to change in order to prevent increased homelessness in the state.

Twenty-eight rental homes are both affordable and available for every 100 renter households that are considered extremely low-income, the report (PDF) from the National Low Income Housing Coalition and Housing Action Illinois found.

Extremely low-income households earn 30 percent or less of the area median income. That’s about $21,650 annually or less.

What the report shows, said Bob Palmer, policy director at Housing Action Illinois, is the private housing market doesn’t work for people with the lowest of incomes.

“It’s impossible for a landlord to make rental units available to people with extremely low incomes and at the same time cover their costs of doing business,” Palmer said. “It’s imperative the public sector provide resources to address this market failure.”

Illinois is one of 13 states below the national level of 30 affordable and available units per 100 households within the extremely low-income threshold, according to the report, “Housing Spotlight: The Shrinking Supply of Affordable Housing” (PDF) .

And no state in the nation has an adequate supply of affordable and available rental housing, the report states.

Julie Dworkin, policy director at the Chicago Coalition for the Homeless, said the lack of affordable, rental housing is the primary cause of homelessness in Illinois and across the country.

“You add on top of that the recession with so many people unemployed,” she said. “You’re going to have more homeless people in these economic times.”

Dworkin added that even in “good economic times” shortages of low-income housing remains an issue.

To combat the shortage of housing in Chicago, the city’s homeless coalition is working on a tax increment financing, or TIF, measure that would award subsidies to private developers that purchase and rehab vacant and foreclosed multi-family properties.

The TIF ordinance was approved in May 2011, but the homeless coalition and the city are still determining what TIF district to test the program in first, Dworkin said.

At the state level, Palmer said there’s about $130 million set aside for low-income housing as part of Illinois’ 2009 capital budget funding, but so far, the money has mostly gone to households in foreclosure, which Housing Action Illinois also supports.

But, Palmer added, “It would be great if some of the money left went specifically to subsidize the rents of extremely low-income households.”

Additionally, housing advocates want to see federal funding trickle down to Illinois from the 2008 National Housing Trust Fund, which targets extremely low-income families.

The National Housing Trust Fund has not yet been financed, but President Barack Obama included $1 billion for the fund in his 2013 budget proposal, released February 13.

“Solving the shortage of affordable rental housing is the most important homelessness prevention measure we can undertake,” said Sheila Crowley, president and CEO of the National Low Income Housing Coalition, in a press release.

“Investing in the National Housing Trust Fund is our best chance of ensuring affordable housing for all Americans.”