The report highlights the significant reduction in affordable rental housing across the United States from 1990 to 2017.  During this period, the number of units renting for under $600 per month (adjusted for inflation) decreased by nearly 4 million, dropping from 46% to 25% of the rental stock.  This decline has exacerbated housing cost burdens for low-income renters, with 82% of such households spending more than 30% of their income on rent by 2017.  The report attributes this trend to market forces, including the difficulty of building new low-cost units and the lack of downward filtering of higher-rent units.  It also notes that the greatest losses occurred in the last five years of the study period, particularly in states with high foreclosure rates. The findings underscore the urgent need for policies to address the growing affordable housing crisis.

Documenting the Long-Run Decline in Low-Cost Rental Units in the US by State | Joint Center for Housing Studies (harvard.edu)