[Originally posted to firearmsreg Aug 19 1996]
Daniel Polsby writes:
McDowall very freely interprets his five-county study as suggestive
of causation. I tend to share the view that one should be slow to
change public policy on the basis of a single study, though one might
say of Lott-Mustard that it amounts to at least 610
McDowall-Loftin-Wiersema studies, as it covers that many times more
counties, to say nothing of controlling for a lot more variables. I
should say, however, that ordinarily the heavy lifting of causation
involves the existence of a theory which models how the world works.
The Lott-Mustard results are generally consistent with such a theory
(the price theory model).
Qualitatively consistent in that an increase in the price of crime was
associated with a decrease in the volume of crime, yes.
Quantitatively consistent, no. Arrest is 5,000 times more likely than
having a CCW holder pull a gun on you. If the criminal considers
these to be equally bad outcomes, then the CCW law increases the cost
by no more than 0.02%. It is absurd to expect a 7% decrease in crime
from such an insignificant change in the cost.
Even if (contrary to what criminals said in the Wright-Rossi study)
criminals are not afraid of police guns but are afraid of victims
guns. The change in the cost is insignificant. If you believe Kleck
there are about 20,000 DGUs in Dade county each year. If you believe
the NCVS it’s more like 500. Either way, the two by CCW holders is
A general point about deterrence theory. The theory doesn’t tell us
when a person who is supposed to be deterred comes to believe that a
threat is credible. It doesn’t assume, in other words, that there
will be a certain number of dead criminals before people start
believing that if they commit a crime they may be shot. Nuclear
deterrence works in exactly the same way; nobody wants to find out
how credible that sort of threat actually is.
Ahem. Since no nation has actually attacked NATO it is reasonable to
suppose that if one did attack NATO there is a good chance of starting
a nuclear war. On the hand with 50,000 or so violent crimes in Dade
county each year and only 2 DGUs by CCW holders it is not reasonable for a
criminal pulling a violent crime to expect to be thwarted by a CCW holder.