My reader was onto something. From the NYT's extensive probe of Iraqi security now:

[I]n some cases the good news is a consequence of bad news: people in neighborhoods have been “takhalasu” an Iraqi word for purged, meaning killed or driven away. More than 35,000 Iraqis have left their homes in Baghdad since the American troop buildup began, humanitarian groups reported.

When you have no one left in your neighborhood to kill, the numbers of sectarian murders tend to go down a little. We're seeing ethnic cleansing slowed but not ended.

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