pursuasive presentation

Pro

It is unlikely that the Supreme Court's recent Second Amendment decision will noticeably affect national gun ownership rates, but it could increase levels in the handful of local areas that had previously banned handguns, such as Washington, D.C., and Chicago. It is therefore worth reviewing what the best evidence indicates about the likely effects of changes in gun availability.

No one is proposing to legalize the possession or acquisition of guns by convicted criminals, which is currently forbidden in every state. Thus, any weakening of legal restrictions on guns in the foreseeable future is likely to pertain only to those individuals not previously convicted of crimes.

This distinction is important because research has consistently indicated that gun possession and use has both violence-increasing and violence-decreasing effects, and that which of these effects dominates depends on whether the guns are possessed or used by criminals or non-criminals. Gun possession among non-criminals has overwhelmingly violence-reducing effects, while gun possession among criminals has mixed effects.

Research has unanimously indicated that defensive gun use is effective. Victims who use guns during crimes are less likely to be injured or lose property than those who use other resistance strategies or do not resist at all — and almost always without wounding or killing the criminal. Victim gun use does not provoke offenders into greater violence, nor does it result in offenders taking guns from victims and using them against the victims.

Gun ownership may also deter some criminals from even attempting some crimes in the first place, for fear of confronting an armed victim. Criminals interviewed in prison indicate they have at times refrained from committing crimes because they believed a potential victim might have a gun. Likewise, crime rates have dropped substantially after highly publicized instances of prospective victims arming themselves, being trained in gun use or using guns against criminals. Further, burglars in the United States are more careful to avoid residences where the victims are home than burglars in nations with lower gun ownership; burglaries against unoccupied homes cannot result in injury to the residents.

Gun availability among non-criminals tends to increase public safety. More guns among non-criminals does provide more guns for criminals to steal, and thus might increase criminal gun levels, but the statistically strongest research indicates that higher overall gun levels have either no net effect on violent-crime rates or mild crime-reducing effects.

Con

One of the most hotly contested issues in the larger debate on gun control is whether guns in a community have a positive or negative effect on crime. Now, as a result of the Heller decision, the issue may be tested, as gun regulations are challenged on Second Amendment grounds in one jurisdiction after another.

If gun regulations are relaxed and more residents of large, crime-prone cities acquire handguns for self-defense, the rates of assault, robbery, and rape will not be noticeably affected. What will be affected is the assailants' choice of weapon. An increase in gun ownership fuels the secondary market by which guns flow to youths and criminals through loans among family and friends, off-the-books sales and theft. Of course, gun prevalence may have other effects as well — if criminals are concerned about encountering an armed victim, they may desist (the "deterrence" argument). But theoretical arguments are not enough to resolve this issue.

Fortunately, the empirical evidence is very strong, thanks to the discovery of a new proxy for gun prevalence. It turns out that the percentage of suicides with guns is very highly correlated with household gun ownership rates, both across jurisdictions and over time. That discovery has opened the door for empirical research that was previously hamstrung by the lack of a good measure of local gun prevalence. Now we know with certainty that in areas where more households own guns, young men are more likely to carry guns, and more robberies and assaults are likely to involve guns. And that is not good news.

Increased gun use will result in a higher murder rate. When an assailant uses a gun instead of a knife or club, it greatly increases the chance that the victim will die. Guns do not cause violence, but they intensify violence. We have found, using long-term studies in large U.S. counties, that an increase in gun prevalence increases the gun murder rate but has no effect on the non-gun murder rate, so the net result is an increase in the overall murder rate. A 10 percent increase in gun prevalence results in a 1-3 percent increase in murders, all other things equal. We were able to rule out the possibility that this result reflects reverse causation, although we cannot be absolutely sure in the absence of randomized field experiments.

Sadly, the Heller decision may provide something akin to a grand experiment with increased gun prevalence.