In September 2019 Elizabeth La Jeunesse, Alexander Hermann, Daniel McCue and Jonathan Spader of the Joint Center for Housing Studies of Harvard University, authored the paper
Documenting the Long-Run Decline in Low-Cost Rental Units in the US by State. In this paper the researchers sought to answer the following questions: “1) has the number of low-cost rental units indeed declined since 1990, and if so, by how much? 2) Over which periods of time did this decline take place? And 3) are there any differences in the size and timing of losses across US states?
The study conducted by the research team at the Joint Center found that for every 100 low income renter households there are only 58 affordable housing units available for them to rent. Overall from 1990 to 2017 the number of rental units available for $600 per month or less declined by 4.0 million units. A monthly rent of $600 is the maximum an individual making $24,000 can afford. This decline is in stark contrast to the 10.9 million overall rental stock growth over the same time period.
The steepest decline in low income housing availability occurred during the 2012-2017 time period. During this 5 year period the amount of rental units available for less than $600 dropped from 14 million to 11 million units. The share of affordable rental housing stock also dropped from around 40% to just 25% during this 5 year period.
Even though there are some variations in losses of rental units in all 50 states all states saw a decline in units. A total of 27 states and the District of Columbia saw almost a 1/3 loss in rental units for less than $600 dollars per month between 1990 and 2017. Only 16 states between the years of 1990 and 2017 saw less than a 20% decline in rental unit shares for less than $600 dollars a month. This decline in readily available affordable rental housing means that more and more low income individuals compete for fewer and fewer low cost rental units.
While the report does not address
rental housing in rural America, other, previous Joint Center reports document
the lack of affordable housing in small towns and farming communities. Rental housing where it is
available, often costs too much.: 41 percent (5 million households) of rural
renters are cost-burdened, meaning they pay more than 30 percent of their
income for housing costs, and 21 percent (2.1 million households) of rural
households that rent pay more than 50 percent of their income for housing.
 Harvard Joint Center for Housing Studies, “America’s Rental Housing.” 2017. http://www.jchs.harvard.edu/sites/default/files/harvard_jchs_americas_rental_housing_2017_0.pdf