Sunday, November 19, 2006

Time for Another Body Count in Iraq

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Last month there was very little discussion of the study published in the Lancet, a highly respected British medical journal, which estimated that 650,000 Iraqis have died since 2003 as a result of the war. The Lancet study too was dismissed as an "October surprise," and it disappeared from the news within days of its publication. But now that the election is over, can we finally discuss it?

I was shocked myself when I saw the figure of 650,000. It seemed huge, much larger than I had imagined possible. It is approximately four times the Iraqi Health Ministry's recent estimate, and twice the figure of 300,000 that is often given as an estimate of the number of people killed by Saddam Hussein during his 23 years of brutal rule.

The Lancet study, with Gilbert Burnham as its lead author, was conducted by some of the same researchers from Johns Hopkins University and Al Mustansiriya University in Baghdad who conducted a previous study in 2004 which estimated that 98,000 people had died. The earlier study was attacked at the time by supporters of the war and was largely ignored by the mainstream news media in the United States, as John Stauber and I noted in our recent book, The Best War Ever: Lies, Damned Lies and the Mess in Iraq (for an excerpt, see the Third Quarter 2006 issue of PR Watch). The new study suggests that some half a million additional lives have been lost in the subsequent two years.

As the Lancet paper explains, this number is an estimate based on statistical sampling of Iraq's population, and due to limitations in the number of people surveyed, it has a fairly wide margin of error. The researchers followed standard scientific procedure and reported their findings using a "95% confidence interval" — a minimum and maximum value derived from statistical analysis which finds a 95 percent probability that the two limiting values enclose the true number. The minimum value in their confidence interval was 392,979, and their maximum value was 942,636, which means that although 650,000 is their most likely estimate, the true number could be substantially lower or higher. Even so, the low end of this range is nearly 400,000, while the high end is nearly a million.

Are these numbers credible? I looked at reactions to the Lancet study from several groups: American political pundits, scientists with expertise in health and mortality research, and Iraqis (as reflected in the views of Iraqis with English-language weblogs). Many of the political pundits (even those with anti-war views) either rejected the study or questioned its conclusions and methodology. The scientists, however, gave it high marks, and most of the Iraqis thought the number sounded like it was in the right ballpark.

What the Study Says

The full Lancet study is available online. Although it is a scientific paper, I found it easy to read and jargon-free. However, a couple of terms might need explanation.

The study uses a "cluster sampling" methodology that is commonly used in health and mortality research, especially in places hit by war or other humanitarian disasters such as floods or earthquakes. The methodology is somewhat less precise — but more cost-effective and practical — than simple random sampling, in which individual members of the population being studied are selected and interviewed at random. Rather than individuals, researchers interview randomly-selected clusters of individuals and use standard statistical techniques to reach conclusions about the entire population. As Daniel Engber explains in Slate magazine, "It's the same basic method used for political polls in America, which estimate the attitudes of millions of people by surveying 1,000 adults."

A survey of this type, in which researchers go out and methodically sample the population being studied, is called "active surveillance" as opposed to "passive surveillance," which relies on information collected by external sources such as government or news reports. Passive surveillance generally tends to produce unrealistically low estimates, because they miss cases in which someone has died but the death has simply gone reported. Consider, for example, the difference between the results that you would get if you attempted to estimate the health impact of tobacco smoking using passive rather than active surveillance. Epidemiologists have repeatedly and conclusively demonstrated that tobacco smoking causes several hundred thousand deaths per year in the United States, but individual cases of smoking-related death are rarely reported as such in newspapers, so you would get a much lower number if you attempted to compile statistics based on newspaper reports alone.

Currently the most comprehensive attempt to compile statistics on Iraqi death using passive surveillance is being done by the Iraq Body Count website, which as of this writing (November 2, 2006) has tallied 45,061 to 50,022 deaths — less than a tenth of the Lancet result. As the Lancet paper itself notes, "Our estimate of excess deaths is far higher than those reported in Iraq through passive surveillance measures. This discrepancy is not unexpected. Data from passive surveillance are rarely complete, even in stable circumstances, and are even less complete during conflict, when access is restricted and fatal events could be intentionally hidden. Aside from Bosnia, we can find no conflict situation where passive surveillance recorded more than 20% of the deaths measured by population-based methods."

Source: AlterNet: War on Iraq: Time for Another Body Count in Iraq

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