Iraqi deaths overestimated, say researchers :
20/10/2006
Researchers at Royal Holloway, University of London and Oxford University have found serious flaws in the survey of Iraqi deaths published last week in the Lancet.
Professor Michael Spagat of Royal Holloway’s Economics Department, and physicists Professor Neil Johnson and Sean Gourley of Oxford University contend that the study’s methodology is fundamentally flawed and will result in an over-estimation of the death toll in Iraq.
The study suffers from "main street bias" by only surveying houses that are located on cross streets next to main roads or on the main road itself. However many Iraqi households do not satisfy this strict criterion and had no chance of being surveyed.
Main street bias inflates casualty estimates since conflict events such as car bombs, drive-by shootings, artillery strikes on insurgent positions, and market place explosions gravitate toward the same neighbourhood types that the researchers surveyed.
This obvious selection bias would not matter if you were conducting a simple survey on immunisation rates for which the methodology was designed. But in short, the closer you are to a main road, the more likely you are to die in violent activity. So if researchers only count people living close to a main road then it comes as no surprise that they will over count the dead.
During email discussions between the Royal Holloway-Oxford team and the Johns Hopkins team conducted through a reporter for Science, for an article published in the journal on Friday 20 October, it became clear that the authors of the study had not implemented a clear, well-defined and justifiable methodology. The Royal Holloway-Oxford team therefore believes that the scientific community should now re-analyze this study in depth.
The team can be reached for comment at:
Professor Michael Spagat: M.Spagat@rhul.ac.uk
Sean Gourley: s.gourley1@physics.ox.ac.uk
Professor Neil Johnson: n.johnson@physics.ox.ac.uk
For more information, visit:
http://www.rhul.ac.uk/economics/Research/conflict-analysis/iraq-mortality/