This data is st00pid. It relies on self-reporting, and the questions are coached to get the "required" result.

A while ago I did an experiment, I found the list of people convicted for typical "homeless" crimes in SF, and did a background search on them. About 90% had extensive crime records in other states, far away from CA.

This is not a definitive result for sure, but it's suggestive.

My understanding is that "living in the same county as your last housing" can mean that you moved to California with enough money to rent a room for a month before running out. Though, I have seen many other surveys that do indicate that most unhoused individuals have lived in the area for an extended period before factors forced them out (https://www.nytimes.com/2019/11/06/us/homeless-population.ht...).

In any event, I feel that metric used by UCSF is really not a good one to the point where it's almost dishonest. It's not hard to come up with questions that do a better job at trying to answer whether CA is burdened by individuals moving from out-of-state to make use of more generous social programs and/or lax drug policy.