Even if it’s true that most unhoused people are mentally ill — and I agree with Tim’s reply — you have must consider causation versus correlation. Is an unhoused person dysfunctional because they were always that way and thus doomed to lose shelter, or are they dysfunctional because living on the streets is extremely damaging?

You see this question a lot when discussing drug usage among homeless. The percentages of addicts is undeniably high; we know this from point in time counts, for example. Some people take that as proof that homelessness is the fault of the homeless: they made the bad decision to take drugs, and that’s why they lost their jobs. But there’s also a lot of data showing that people are more likely to become addicted as a way to cope with street life.

And if, in fact, losing your home is something that can happen relatively easily in part because of wealth inequality, we’re right back to the original assertion.

Underbuilding is for sure another factor. It’s just not the only one.