Well, I have no way to prove my experience through data, since it's not being taken by any reputable sources I know of, sadly...

But what I can say at least is that I would suspect that the 'drug slum' aspect occurs because the drug users flock towards those needle exchanges and congregate near them for convenience sake. I say that, because that's what seemed to be the case when I lived in those areas. People I never saw in those neighborhoods before, suddenly practically lived there. So I suspect that is the case.

Anyways, it's getting late and my patience is starting to wear thin, so I should probably go now before nicer folk like you start to think of me as less well reasoned and less articulate a person.