By Professor Kelly M. Greenhill, Tufts and Harvard (KSG) universities
Can we ever know how many died as a result of the 2003 Iraq war?
How many people have died as a result of the 2003 war in Iraq and the post-war occupation? The answer is unknown - and probably unknowable - but not because no-one has tried to count the dead.
There are a number of casualty estimates but they vary profoundly and have been highly contentious. The lowest estimates place the death toll at fewer than 100,000 (still a large number, of course) while the highest suggest the toll might exceed 1.4 million. This enormous variation is attributable in large part to three distinct problems.
Counting during conflicts
The first is data acquisition. Counting the dead amid ongoing violence is difficult and often risky. Fatalities frequently occur in dangerous and inaccessible places, among hostile parties, and under chaotic conditions.
Hospital and morgue reporting systems are often disrupted or undermined in wartime. Separating combatants from non-combatants can be very difficult - particularly in an unconventional and asymmetric conflict like the war in Iraq.
Prof Greenhill spoke to More or Less about Iraq war casualty estimates
A second reason estimates vary so significantly is related to measurement disparities and inconsistencies. Different sources and studies have examined different periods of time. This variation has significant implications, given that levels of violence have waxed and waned tremendously in the period since the invasion, with the years 2006 and 2007 the deadliest by a wide margin.
Different definitions of what constitutes a war-related fatality have also been used. Some estimates include combatants, while others focus solely on civilians. Some include indirect deaths, while others only count violent, intentional deaths. The disparities inherent in these 'apples versus oranges' comparisons are made still more acute by the fact that definitions of what constitutes "violent" and "non-violent" causes of death also vary across studies.
"Passive surveillance" techniques
Perhaps most critically, fundamentally different methods for counting the dead have been used. Employing what are called "passive surveillance" techniques, the UK-based research group
Iraq Body Count (IBC)
has cross-referenced fatalities reported in the media with figures from Iraqi hospitals, morgues and NGOs and estimate there to have been approximately 100,000 violent civilian deaths since 2003.
IBC expects to raise this tally by about 19 percent, reflecting new data gleaned from classified US government documents released by Wikileaks late last year. IBC acknowledges that their figures are probably underestimates, because passive techniques tend to suffer from under-counting and under-reporting.
However, their numbers largely agree with those offered by the Washington-based
Brookings Institution's 'Iraq Index'
, which also employs passive techniques, but relies on a different bundle of sources.
The documents released by Wikileaks also suggest that the US has recorded over 150,000 violent deaths since March 2003, more than 80 percent of which have been civilians, which places the US Government's own estimate in the same range.
"Active survey" techniques
Significantly higher estimates have emerged from studies employing "active survey" techniques. At least four household surveys have been conducted in Iraq.
In each, Iraqis were asked to identify the number of family members they had lost and, in some cases, to provide documentation to support their claims. (In some cases it appears survey respondents' answers were limited to immediate family members, while in others they included extended family members.)
Survey results were then extrapolated to generate nationwide estimates ranging from several hundred thousand, in a generally well-regarded
World Health Organization-sponsored study
, to well over a million, in a more contentious study undertaken by a group called
Opinion Research Business (ORB).
Arguably, the most widely publicized - and most broadly criticized - of the survey studies was conducted by researchers from Johns Hopkins University in Baltimore.
In results published in the
, they suggested that war-related deaths, broadly defined, numbered between about 400,000 to just under 800,000. Although these figures are significantly lower than ORB estimates, they still dwarf the WHO study numbers.
There are two key reasons why the WHO study is viewed as more authoritative. First, external analysis of its dataset has successfully withstood more expert scrutiny. Second, its survey teams interviewed about five times as many people as the ORB team; a larger study sample size reduces the risk that deaths are over- or under-represented in the data.
Even taking data acquisition difficulties and measurement disparities into account, however, the range of estimates is simply huge. This sizable gap is a key reason why claims of a third factor - namely politics - enters the picture.
Arriving at a reasonable estimate
The truth is we cannot realistically identify the precise number of Iraqi war dead. However, by relying on the aggregate assessments of objective third parties, employing common sense and undertaking some basic back-of-the-envelope calculations, the range of reasonable estimates can be reduced.
Although passive surveillance techniques have clear limitations, taken together the relatively similar estimates of IBC, Brookings, et al., represent a defensible lower-end estimate of approximately 110,000-125,000 violent civilian deaths since the US-led invasion.
Monthly tallies from the start of the invasion through to early 2011 show approximately 45 percent of these fatalities occurred before the end of June 2006 and 55 percent afterwards.
If one applies the same 45:55 ratio to the WHO March 2003-June 2006 figure of 151,000, allows for the possibility that WHO's reliance on some passive surveillance data for areas deemed too dangerous to visit may have resulted in some undercounting, and takes account of 'Wikileaked' US government documents, a current high-end estimate can also be derived: a ceiling of about 400,000 civilian fatalities.
The gap between 125,000 and 400,000 is still wide, and this estimate too must be treated with caution. Whatever the true figure, the suffering is not over yet. While the death rate in Iraq has plunged of late, the toll is at least 4,000 higher than it was this time last year.
Kelly Greenhill is co-editor of the book
Sex, Drugs and Body Counts: The Politics of Numbers in Global Crime and Conflict.