Thoughts on the surge and ethnic cleansing

While it's common now to hear reports of the surge working, I'm curious to know how much the drop in violence correlates to the ethnic cleansing that's been happening in Iraq for the past few years. All of the Iraqi on Iraqi violence is purposeful, i.e. designed to drive the Sunni out of Shia neighborhoods and vice versa. What if the militias and insurgents are just wrapping up the ethnic cleansing and there's no one handy to kill?

I imagine it's hard to find mixed neighborhoods these days, which would make the murders and bombings more difficult to commit. A good way to test the theory would be to see if inter-ethnic violence increases as extra-ethnic violence decreases. The recent tribal push against AQ is some evidence of that as without readily available Shia AQ has nothing to offer the Sunni tribes.

So many questions, so little data. I guess another way of putting it is "what if Iraq completed it's civil war while everyone was debating the meaning of "Civil War"? (note, I still dislike the term to refer to the conflict, Gang war is the better term.).