The Joint Center for Housing Studies of Harvard University released a working paper, which details the dramatic decline of low-cost rental units over the past three decades. The number of units renting for less than $600 per month, adjusted for inflation, fell by almost 4 million between 1990 and 2017. The data also show that this decline was concentrated in the last five years. After falling modestly in the 1990s and early 2000s, the stock of low-cost units rose in the aftermath of the recession. Since 2012, however, the number of units renting for under $600 has fallen sharply, accounting for a large share of the decline in low-cost units over the long run.