By Samuel H. Preston and Emily Buzzell
Saturday, August 26, 2006
The consequences of Operation Iraqi Freedom for U.S. forces are being documented by the Defense Department with an exceptional degree of openness and transparency. Its daily and cumulative counts of deaths receive a great deal of publicity. But deaths alone don't indicate the risk for an individual. For this purpose, the number of deaths must be compared with the number of individuals exposed to the risk of death. The Defense Department has supplied us with appropriate data on exposure, and we take advantage of it to provide the first profile of military mortality in Iraq.
Between March 21, 2003, when the first military death was recorded in Iraq, and March 31, 2006, there were 2,321 deaths among American troops in Iraq. Seventy-nine percent were a result of action by hostile forces. Troops spent a total of 592,002 "person-years" in Iraq during this period. The ratio of deaths to person-years, .00392, or 3.92 deaths per 1,000 person-years, is the death rate of military personnel in Iraq.
How does this rate compare with that in other groups? One meaningful comparison is to the civilian population of the United States. That rate was 8.42 per 1,000 in 2003, more than twice that for military personnel in Iraq.
The comparison is imperfect, of course, because a much higher fraction of the American population is elderly and subject to higher death rates from degenerative diseases. The death rate for U.S. men ages 18 to 39 in 2003 was 1.53 per 1,000 -- 39 percent of that of troops in Iraq. But one can also find something equivalent to combat conditions on home soil. The death rate for African American men ages 20 to 34 in Philadelphia was 4.37 per 1,000 in 2002, 11 percent higher than among troops in Iraq. Slightly more than half the Philadelphia deaths were homicides.
The death rate of American troops in Vietnam was 5.6 times that observed in Iraq. Part of the reduction in the death rate is attributable to improvements in military medicine and such things as the use of body armor. These have reduced the ratio of deaths to wounds from 24 percent in Vietnam to 13 percent in Iraq. Some other factors to be considered:
Branch of service: Marines are paying the highest toll in Iraq. Their death rate is more than double that of the Army, 10 times higher than that of the Navy and 20 times higher than for the Air Force. In fact, those in the Navy and Air Force have substantially lower death rates than civilian men ages 20 to 34.
Among the Marines, there is in effect no difference in the mortality risks for members on active duty and those in the reserve. In the Army, on the other hand, reservists have 33 percent of the death rate of those in active service because they are not assigned to combat positions. Members of the Army National Guard are intermediate in assignments and in mortality.
Rank: In both the Army and the Marines, enlisted personnel have 40 percent higher mortality than officers. The excess mortality of enlisted soldiers is diminished by the high mortality of the lowest-ranking officers, lieutenants, who are typically the leaders of combat patrols. Lieutenants have the highest mortality of any rank in the Army, 19 percent higher than all Army troops combined. Marine Corps lieutenants have 11 percent higher mortality than all Marines. But the single highest-mortality group in any service consists of lance corporals in the Marines, whose death risk is 3.3 times that of all troops in Iraq.
Age, sex , race and ethnicity: In contrast to the civilian population, mortality rates decline precipitously with age. Troops ages 17 to 19 have a death risk 4.6 times that of those 50 and older. Differences in rank by age undoubtedly contribute to this pattern, and so do differences in branch of service. Sixty-five percent of Marine deployments to Iraq were of those age 24 or younger, compared with only 39 percent of Army deployments. Women are not assigned to combat specialties in Iraq, although they do see enemy fire; their death rate is 18 percent that of men.
Identifying racial and ethnic differences in mortality is not straightforward because the Defense Department uses a different classification system for deaths than for deployments. Nevertheless, all attempts we have made to reconcile the two systems reach the same conclusion: Hispanics have a death risk about 20 percent higher than non-Hispanics, and blacks have a death risk about 30 to 40 percent lower than that of non-blacks. That low death rate appears to result from an overrepresentation of blacks in low-risk categories: For example, 19 percent of blacks in Iraq are women, compared with 9 percent of non-blacks, while 7 percent of blacks in Iraq are Marines, compared with 13 percent of non-blacks.
Other casualties: The number of wounded in Iraq through March 31, 2006, was 7.5 times the number of dead; the rate at which wounds are incurred was one per 33 troops per year. We do not have the same information about the characteristics of those wounded as we have about those killed. But given the overwhelming importance of hostile encounters in both wounds and deaths, it is likely that variations in the risk of being wounded are quite similar to those presented here.
Samuel H. Preston is the Frederick J. Warren professor of demography at the University of Pennsylvania. Emily Buzzell is a student in the Health and Societies Program at Penn.