Recent American military data indicates that for the fourth week in a row, the nationwide weekly number of attacks is at its lowest level since January 2006. The number of civilians killed, as measured by the American and Iraqi governments, continued to decline in November. The number of weekly casualties, wounded as well as killed, suffered by Iraqi civilians, Iraqi forces and American forces, increased last week by 56 percent but was still below the level for most of 2006 and 2007.

The military also lowered its tally of how many Iraqis had joined neighborhood watch groups. The new figure for Concerned Local Citizens, as the military calls the volunteers, is 60,321. The previous estimate of 77,000 erroneously combined the number of volunteers who are currently serving with those who had expressed a willingness to join.

Col. Martin Stanton, who oversaw the count, said he told General Petraeus about the new figures this week.

Military officials said that they were seeking to make greater use of some Iraqi government data to provide a more comprehensive portrayal of the situation in Iraq. Though there are concerns about the reliability of some Iraqi reports, American military data generally understates Iraqi civilian deaths, since American units only report what they observe, officials said. At General Petraeus’s recommendation, the Pentagon is expected for the first time to include the Iraqi government data on civilian deaths in its report next month on security trends in Iraq.

Image A mother led her daughter to a car waiting in Baghdads Mansour neighborhood Sunday after arriving from Damascus, Syria. Credit... Michael Kamber for The New York Times

While there is no question that large numbers of Iraqis have left their homes, American officials said that the exact number is not available. The International Organization for Migration has reported that the number of internally “displaced” Iraqis — those who have fled their homes but still live in Iraq — has grown to more than one million since the February 2006 bombing of a Shiite shrine in Samarra. Among those displaced Iraqis, more than 350,000 live in Baghdad Province, according to estimates by humanitarian organizations.

Estimates by the Iraqi Red Crescent of the number of displaced Iraqis run much higher, but are marred by the double and triple counting of Iraqis who move from one area to another, American officials say. One difficulty in fixing an accurate count is that many displaced Iraqis do not register their migrant status with Iraqi authorities, American officials said.