When Gen. David Petraeus testifies before Congress next week, he's expected to credit the "surge" with a 75 percent reduction in sectarian violence across Iraq.

How does Petraeus come up with such a gaudy number when the Government Accountability Office says it's "unclear whether sectarian violence has decreased" at all?

As we noted yesterday, the Pentagon says that the GAO didn't have access to statistics from August, when it claims that things really turned around dramatically. But as the Washington Post reports today, there's more to it than that: Petraeus can say that there's been a dramatic drop in all kinds of violence in Iraq because he doesn't count ... all kinds of violence in Iraq.

The increasing number of attacks between rival Shiite militias in southern Iraq? A spokesman for the Multi-National Force-Iraq tells the Post that they're not included in the military's statistics because of the "lack of capability to accurately track" either Shiite-on-Shiite or Sunni-on-Sunni violence, "except in certain instances."

The attacks by Sunni tribesman, supposedly aligned with the U.S. troops in fighting Iraqis allegedly aligned with al-Qaida? Those aren't included either, the military says.

Other sectarian attacks are counted, but not sometimes, arbitrarily. A senior intelligence official familiar with the military's math says attacks in which a victim was shot through the back of the head would be deemed "sectarian." If the victim was shot through the front of the head, it's just a garden-variety "criminal" attack.

So what do the real numbers look like? As the Post notes, the military stopped releasing statistics on civilian deaths in 2005 because it thought the press back home was taking them out of context. When the Post asked this week for month-by-month figures, an MNF-I spokesman said that "exact monthly figures cannot be provided" for the last two years, but insisted that the trends were favorable.

Favorable trends? The Associated Press tries to track civilian casualties in Iraq, and it reported last week that 1,809 Iraqi civilians were killed in August. That's down just a bit from July, when 1,967 civilians were killed, but it's higher than the death toll from June.

More to the point, the AP's August number is only 17 percent smaller than the death toll it counted when sectarian violence peaked in December 2006 -- which is to say, just before the "surge" began.