The shortage of homes affordable to the nation’s poorest households grew significantly last year, according to new research by the National Low Income Housing Coalition (NLIHC).

In 2007, the shortage of homes affordable to extremely low-income families, those earning 30 percent or less of the area median income, was 2.7 million. The shortage swelled to 3.1 million in 2008.

NLIHC officials say the deficit of rental homes that are affordable to the poorest households is getting worse because of the number of extremely low-income households is increasing, while the number of rental homes they can afford dwindles. An analysis of the 2008 American Community Survey shows that the number of all renter households in the nation grew by 2.4 percent between 2007 and 2008. However, the number of extremely low-income renter households increased by 3.5 percent. During the same period, the supply of all rental homes increased by 2.2 percent, but the supply of rental homes affordable to extremely low-income families fell by 1.8 percent.

The reality is even worse, according to the NLIHC, which points out that many of the homes that extremely low-income families can afford are occupied by higher-income people. For every 100 extremely low-income renter households, there were 39 rental housing units affordable and available to them in 2007. By 2008, the number of affordable and available units was just 37.

The shortage will likely be worse this year and next as a result of the increase in unemployment, which is pushing more households to compete for affordable housing.

NLIHC leaders and other advocates have been calling on Congress to fund the National Housing Trust Fund with at least $1 billion by the end of the year.