Interesting. The Pew Research linked to by the OP has a lot more detail:

https://www.pew.org/en/research-and-analysis/issue-briefs/20...

This passage, in particular, is eye-opening:

> ... had SROs [single-room occupancies] grown since 1960 at about the same rate as the rest of the U.S. housing stock, the nation would have roughly 2.5 million more such units— enough to house every American experiencing homelessness in a recent federal count more than three times over.