Could the apparent success of The Surge be partially the result of just the process of Ethnic Cleansing/Sectarian Violence?

As an economist/mathematician, it strikes me that there must be a natural limit to the process of Ethnic Cleansing/Sectarian Violence - - if it works, the participants move to their own enclaves or they are killed or disabled. It seems that it may not take all that long for the players to readjust their circumstances and for things to settle down. Is this a factor in the apparent success of The Suge, which is just not mentioned in the national media? Was our timing of The Surge just coincidental with the end of an Ethnic Cleansing process in various Iraq neighborhoods?