Kellermann's case-control study on gun ownership and homicide

Edgar Suter writes:

In Kellermann's most recent study of homicide (Kellermann et al. "Gun
Ownership as a Risk Factor for Homicide in the Home." NEJM Oct 7, 1993;
329(15):1084-1091.) notes "Two hundred nine victims (49.8 percent) died from
gunshot wounds." Prof. Schaffer offers a robust [and successful] effort to
show that the "gun in the home" cannot be the actual homicide instrument in
every case. According to Table 1, mentioned by Mr. Lambert, this figure
includes 1% "unknown firearm" as "method of homicide." Let's charitably
imagine that these "unknown firearms" actually were the "gun in the home."
Let's charitably imagine that all of the "handgun," "rifle," and "shotgun"
methods tabulated were "guns in the home." Let's accept the unlikely
assumption that not one gun was imported into the home for the homicide.

Still a majority of the homicides were not committed by guns, so could not
have been committed by Kellermann's scary "guns in the home." How then did
the "gun in the home" become a risk factor for homicide.

Because a significant number of the homicides were committed with the
gun in the home.

I can imagine no
explanation for such a phenomenon other than by invoking silly
anthropomorphic magical thinking --- the "magnetize murderers to the doorstep"
silliness.

You cannot imagine the possibility that someone would use a gun in the
home for murder?

Can anyone offer a reasonable hypothesis to explain how a "gun in the home"
can increase the risk of being killed by strangulation, stabbing, etc.?

I cannot offer such a hypothesis. Of course, since the the study
indicates that a "gun in the home" was not associated with an increased
risk of being killed by strangulation, stabbing, such a hypothesis is
not needed.

Kellermann asserts that the "gun in the home"is a risk factor in that paper
and, as Prof. Polsby noted, was "less diffident" in his post-publication
comments. Explaining how "guns in the home" increase non-firearms deaths,
since it is clearly part of the "risk" Kellermann invokes, certainly "bear
relation to the content of the paper."

Except that Kellermann only found an increased risk of firearm deaths.

You have apparently found the method for distinguishing between cause
and effect that eluded Dr Kellermann.

Yes, I have. "...in context with all the other scientific evidence..." I
simply avoid Kellermann's self-citations and incestuous citation of only the
congenial "public health" literature. In reviewing not only the studies that
Kellermann finds congenial, but also the literature that he finds uncongenial
or ignores, the correct order of causality can be deduced -- and is the only
order of causality that does not require invoking any magical thinking. The
studies that show an inverse relationship between gun density and crime
disallow the "guns cause crime" hypothesis.

The relevant hypothesis is "guns make crime more deadly". The
scientific evidence on this is never going to be conclusive, but it
certainly tends to support it. For example, Kleck found that "gun
present" was associated with a 1.4% increase in the risk of death in
violent incidents (Point Blank table 5.11). Knives were associated
with a very much smaller increased risk (0.3%).

Can you tell us how you were able to eliminate the possibility that
injured crime victims may find it more difficult to resist?

Certainly a possibility, but of what relevance? Looking at endpoints, gun
defenders have fewer injuries than non-resistance or resistance with less
powerful means.

Or, to put it another way, those that are injured are less likely to
use guns. Does gun use prevent injury? Or does injury prevent gun
use? Which is the cause and which is the effect? Correlation alone
cannot decide this.

Or the possibility that high crime rates might cause states to enact
controls on handgun carry?

Please note Clayton's earlier post about the admixture of high, average, and
low crime states among the reformed states.

This just means that the correlation is not that strong. It does not
help us disentangle cause and effect.

Clayton does properly challenge my use of "static" data. In a "more
diffident" context I offer the "every category of crime... is lower"
comparison only to undercut the anti-self-defense lobby's claim that
progressive carry reform "will" or "might" lead to "blood running in the
streets." While the static observation does not allow me to make a claim of
a causal relationship (that carry causes lower crime), the observation does
undercut the anti-self-defense lobby's claim that carry increases crime
(particularly when coupled with Cramer & Kopel's data). I should have made
the less expansive claim, "All this may_explain [rather than my original
"explains"] why the 28 states that allow law-abiding, mentally-competent
adults to protect themselves outside the home with concealed handguns have
lower rates of crime for every category of crime indexed by the FBI." Mea
culpa.

Based on the data you presented, I find that the average homicide rate
in the permissive carry states is 7.9 and in the restrictive states it
is 10.2.

States with low populations tend to have low homicide rates and
permissive laws. This is the reason why the average is lower in the
permissive states. If we control for the size of the state's
population by just considering states with populations between 1 and
10 million we find that the average in the permissive states (8.3) is
very slightly higher than in the restrictive states (8.2). (There are
too few restrictive low population states and too few permissive low
population states for meaningful comparison amongst high and low
population states.)

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