Gun control opponents often make the claim that no scientific study has ever proven that gun control law caused a reduction in violent crime. The suggestion is that gun control laws are irrational, and that proponents are either ignorant and paranoid or, more ominously, looking for a way to oppress the population. But is this claim and its conclusions fair? Let’s look closer.
As most social scientists can attest, it is very difficult to design a social study which conclusively proves a specific effect of a singular aspect in society at large. That is because society is complex and changing, with observables constantly being influenced by multiple variables with complex interactions.
You may try to compare different societies that seem similar – and this has been done. There is a high correlation between violent crime rates and availability of handguns (3), a correlation which easily beats any statistical error. But correlation does not prove causation: it is just as possible that societies with high levels of violence seek to arm themselves with guns, rather than the guns causing the violence.
Another strategy may be to compare the same society against itself in the past against a time when gun control laws were different. But you essentially run into the same problem – once you move through time, you are changing variables that are important to what you are trying to measure, without knowing exactly what they are and how they affect your results. For example, studies have shown that violent crime levels in Australia has reduced since the enactment of strict gun controls (4). But crime rates have been falling even before the laws were enacted. It was not necessarily gun control laws that caused the drop in violent crime, but some other factor like better welfare or economic growth.
Another approach is to compare various groups within the same society. At least one researcher compared homicide rates between young adults and older teens in a society where young adults are allowed to carry firearms, and teens not (2). His conclusion was that homicide rates increased for the gun-carrying age group. Once again, the gun owners argue, you can’t compare apples and pears. There may be other reasons why young adults in this country are prone to being murdered than teenagers.
In fact, a one important study on the effect of gun control came to the inevitable conclusion that there may not exist a statistical method that can settle this question one way or another. In “Firearms and Violence: A Critical Review” Appendix D: Statistical Issues in the Evaluation of Right-to-Carry Laws (1), the researchers state:
“..there is little likelihood that persuasive conclusions about the effects of right-to-carry laws can be drawn from analyses of observational (nonexperimental) data.”
Without the ability to experiment (which is morally dubious) or isolate individuals within a society (because gun violence affects everybody, not just classifiable individuals), researchers are basically saying that it is impossible to declare with certainty that gun control laws have either a positive or negative effect on violent crime rates. They do not state that there is no causative relationship – they state that this relationship is not provable.
This is a far weaker conclusion than what pro-gun lobbyists would have you believe. Their claim is technically true, as no study has conclusively *proven* that gun control laws reduces violent crime, but that is because the conditions for proof is difficult to obtain for such a complex study. It is unjustifiable to suggest that this settles the debate.
(2) Ludwig, J. 1998: "Concealed Gun-Carrying Laws and Violent Crime: Evidence from State Panel Data." International Review of Law and Economics, 18, 239-254.
(3) Carter, G.L. 1997: The Gun Control Movement. New York: Twayne Publishers.