Kellermann’s studies on guns frequently get criticized by people who do not seem to have read them. The latest to do so is Michael Krauss, who writes
Notwithstanding all this data, the press gave extraordinary publicity to a 1993 article by one Arthur Kellerman in the New England Journal of Medicine. Kellerman’s “study” concluded that the presence of a gun in one’s home dramatically increased one’s chances of being killed by gunfire. As has since been widely noted, though, the study had stupendous methodological flaws that would surely have precluded its publication, were the NEJM not blinded by its fear and loathing of guns.
As we shall see below, Krauss doesn’t seem to have actually read Kellermann‘s study.
The study consisted of going to homes where a homicide occurred, and asking whether there was a gun in the house. Such a study by design and definition excluded successful uses of the gun (i.e., where the attacker is scared off and no one is killed).
Not so. Krauss is apparently unaware that the study was a case-control study. That means that as well as visiting the houses where there was a homicide (the cases), they also found similar homes where there wasn’t a homicide (the controls). Successful uses of guns that prevent homicides show up in the controls.
Even if the homicide victim was someone who did not live in the house, and who was stabbed to death, the answer “yes” to the question, “Was there a gun in the house?”, would increase the correlation between guns and homicide.
Krauss does not seem to have even bothered to look at the abstract of the study. It states: “we identified homicides occurring in the homes of victims”.
Moreover, the fear of being killed by a stalker or a gang might well contribute to one’s decision to purchase a firearm. If the fear is well-founded, then we would expect gun purchasers to be more likely victims of murder than others. But that does not establish that the firearm ownership caused the crime. Analogously to Kellerman’s dishonest methodology, I could “prove” that visiting a hospital correlates with dying. This does not show that the hospital visit caused the fatal illness.
Krauss seems to be unaware that Kellermann’s study controlled for many factors such as age, sex, neighbourhood, drug use and criminal history. To take the hospital example, if we compare people with the same disease and the same severity of disease and find that the ones who go to hospital are more likely to die than the ones that don’t then you have evidence that the hospital is making things worse. Furthermore, Kellermann’s study found that gun ownership was not associated with a higher risk of being murdered by other means, just with a higher risk of being murdered with a gun. Are we supposed to believe that people only get a gun to defend against potential killers that are going to use guns and not against people who might attack them with a knife?
I would have hoped that before making serious charges of dishonesty against Kellermann, Krauss would have looked at Kellermann’s study, but he does not seem to have done so. And Krauss is a law professor.