Between drug addiction and mental illness, it's not 'more like half', but hey - let's say it is - doesn't it bother you that the current policies are created with the assumption that homelessness is an income problem? That, therefore, 'more like half' of the homeless population is not helped by the billions of dollars being spent on combating homelessness?

25% of the homeless are seriously mentally ill according to the most extensive survey ever done by HUD.

35% have a substance abuse problem.

Believing that these populations don't overlap involves some pretty magical thinking. Logically between 40-50% have one or the other problem and 10-20% have both problems.

This doesn't however paint a complete picture because its a chicken and egg situation. Did people end up homeless because they were ill or on drugs or did they end up ill and or on drugs after they were on the street.