The good people over at TPM filed a Freedom of Information Act request to find out exactly what counting system General Petraeus was using when he went before Congress and said that sectarian violence is down in Iraq. A number of independent assessments and outside experts either contradicted his claims or threw serious doubt on them.
Here are some answers. First, any violence perpetrated by Sunnis on other Sunnis or by Shiites or other Shiites doesn't count. While that seems like a natural enough thing to exclude from a definition of "sectarian violence," it means that the general level of crime/lawlessness in Iraq is scrubbed out of Petraeus' numbers. It also means that when the sect of a perpetrator of a violent crime isn't immediately obvious, the authorities have the ability to do some investigating and deducing, and then to label the attack as either sectarian or non-sectarian. And those authorities, be they Iraqi or American, absolutely have an agenda.
Second, attacks on U.S. forces don't count. Again, a reasonable thing to exclude from a tabulation of sectarian attacks. But Petraeus should have presented statistics on the number of attacks on U.S. forces with the same frequency and prominence that he presented stats on sectarian violence.
Third, attacks on the Iraqi government or Iraqi security forces are not included. This is just preposterous. The Shiites control the government and have infiltrated the security forces. The Sunnis insurgents had control of the country for decades and are now on the outs. This can't be stressed enough: when insurgents attack the government, their intentions are sectarian. Whatever other motivations there might be, they cannot be teased out from sect-based hatred and jockeying for power.
When Sunni insurgents attack the government or the government's corrupt goons in uniform, they do so because their targets are Shiites. That's reality. When the Army believes otherwise it is an act of willful ignorance meant to deceive the American people.