The overwhelmingly vast majority migrate. Some of them might have had a sublet apartment or lived at a friend's couch for a while before becoming homeless. So

The overwhelmingly vast majority migrate. Some of them might have had a sublet apartment or lived at a friend's couch for a while before becoming homeless. So the statistics say "most homeless lived in SF prior to becoming homeless", but if you actually check local school records you know they didn't grow up here.