So what accounts for the difference? Katulis says he doesn't know, and hasn't been able to get an answer from the Pentagon. Two possibilities present themselves: either Multinational Corps-Iraq, from whose database the statistics emerged, changed its definition of "sectarian" incidents and murders; or new information became available after March. Whatever the answer, a reader of the June report doesn't have any way of knowing that the March report gave different statistics on sectarianism.
Similarly, the November 2006 report (pdf) contains seven mentions of the term "death squads." ("Armed groups that conduct extra-judicial killings" is the definition given by the November report.) Yet in March, the term only appears once, with no given definition -- it appears in scare quotes, even -- and in June, the term vanishes from the report's lexicon. Again, there's no stated reason why the term vanishes: it's not as if Iraq is suddenly free from death squads. In many cases, as the draft GAO report leaked to The Washington Post today reveals, they've embedded within the Iraqi security forces we're building.
The question immediately raised by the retroactive changes in statistics on sectarianism and other key measures is whether the next quarterly report, due in September, will similarly juggle the data without notifying readers to the change. "We have to be able to understand the models, and have an apples-to-apples comparison," Katulis says, in order to make sense of what Dubik called the "mosaic" of Iraq. Right now, the quarterly Pentagon report looks less like a mosaic than it does a Rorshach test.