My understanding is a lot of it is voluntary migration. If you you're not paying rent, you don't have a job, and you've burned all your social support ties, you

My understanding is a lot of it is voluntary migration. If you you're not paying rent, you don't have a job, and you've burned all your social support ties, you might as well get a greyhound to a place with good weather, good social services, and where people will look the other way on your visible symptoms of mental illness and drug addictions.