Reply from author of Lancet report. posted by Richard Seymour

The research published in the Lancet claiming a conservative estimate of 100,000 excess deaths as a result of the war on Iraq prompted innumerable 'ah but' replies, claiming that there was something wrong with the research or that it was shoddy or too vague, as well as criticisms of the Lancet from people who have no idea what kind of publication it is and would never in their lives have dreamed of picking up a copy of what is essentially a robustly conservative medical journal. Notable among the former was Fred Kaplan's piece for Slate . It contained many criticisms directed at points already accounted for in the report, but the key issue he raised was as follows:

The report's authors derive this figure by estimating how many Iraqis died in a 14-month period before the U.S. invasion, conducting surveys on how many died in a similar period after the invasion began (more on those surveys later), and subtracting the difference. That difference—the number of "extra" deaths in the post-invasion period—signifies the war's toll. That number is 98,000. But read the passage that cites the calculation more fully:

We estimate there were 98,000 extra deaths (95% CI 8000-194 000) during the post-war period.

Readers who are accustomed to perusing statistical documents know what the set of numbers in the parentheses means. For the other 99.9 percent of you, I'll spell it out in plain English—which, disturbingly, the study never does. It means that the authors are 95 percent confident that the war-caused deaths totaled some number between 8,000 and 194,000. (The number cited in plain language—98,000—is roughly at the halfway point in this absurdly vast range.)

This isn't an estimate. It's a dart board.

This would seem on the face of it to be quite a damning point - research producing conclusions so vague that settling on any one interpretation seems quite arbitrary. Unfortunately, and more or less as I expected, Kaplan did not understand the nature of the research. Correspondence with one of the report's authors has yielded the following:

By Richard Garfield, one of the study's authors.

On page five of the report. second to last paragraph, the authors do
give us
a margin of sampling error. They have not found a hard-and-fast 98,000
additional deaths, but a range from 8,000 to 194,000.


That is correct. Research is more than summarizing data, it is also
interpretation. If we had just visited the 32 neighborhoods without
Falluja and did not look at the data or think about them, we would have
reported 98,000 deaths, and said the measure was so imprecise that there
was a 2.5% chance that there had been less than 8,000 deaths, a 10%
chance that there had been less than about 45,000 deaths,....all of
those assumptions that go with normal distributions. But we had two
other pieces of information. First, violence accounted for only 2% of
deaths before the war and was the main cause of death after the
invasion. That is
something new, consistent with the dramatic rise in mortality and
reduces the likelihood that
the true number was at the lower end of the confidence range. Secondly,
there is the Falluja
data, which imply that there are pockets of Anbar, or other communities
like Falluja, experiencing intense conflict, that have far more deaths
than the rest of the country. We set that aside these data in
statistical analysis because the result in this cluster was such an
outlier, but it tells us that the true death toll is
far more likely to be on the high-side of our point estimate than on the
low side.

Further comment would be superfluous.