GunsMathematical model informs gun policy debate

The relationship between the legal availability of guns and the firearm-related homicide rate has been a hot topic of debate in the United States for more than three decades now. Gun-control advocates argue that unrestricted gun availability promotes the occurrence of firearm-induced homicides. Gun-rights supporters have pointed out that gun possession can protect potential victims when attacked.

A new paper provides a first mathematical analysis of this tradeoff. The authors say their goal is to steer the debate toward arguing about assumptions, statistics, and scientific methods. Their model is based on a set of clearly defined assumptions, which are supported by available statistical data, and is formulated axiomatically such that results do not depend on arbitrary mathematical expressions.

The paper examines three possible policies:

• A strict no-guns policy which would decrease the overall number of available guns and, therefore — and by definition — would decrease gun use (and, as a result, gun homicides)
• A guns-for-all policy which would allow anyone to own a gun, thus arming potential victims and possibly deterring criminals from attacking in the first place
• The middle ground, which is the current situation: a moderate gun policy in which certain kinds of guns are available to some people under certain circumstances

The model presented in the paper finds that the only way meaningfully to minimize gun-related homicides rate is to adopt one of the two extreme strategies — either a complete ban on guns or a guns-for-all policy. The middle-ground policy results in a higher homicide rate than either of the two extreme policies.

Importantly, the model identifies the crucial parameters that determine which policy minimizes the death rate, and thus serves as a guide for the design of future epidemiological studies. The parameters that need to be measured include:

• The fraction of offenders that illegally possess a gun
• The degree of protection provided by gun ownership
• The fraction of the population who take up their right to own a gun and carry it when attacked

The limited data available in the literature were used to demonstrate how the model can be parameterized, and, as said above, this preliminary analysis suggests that a ban of private firearm possession, or possibly a partial reduction in gun availability, might lower the rate of firearm-induced homicides.

The authors say that this, however, should not be seen as a policy recommendation due to the limited data available to inform and parameterize the model. The model, however, clearly defines what needs to be measured, and provides a basis for a scientific discussion about assumptions and data.

The authors say that the model is thus as a first step toward a scientific and logical formulation of the issues involved in the gun control debate. Such a formulation should guide the design of future epidemiological studies, and allow the gun control debate to be based on scientific methods and the gathering and interpretation of data rather than on anecdotal evidence and single, dramatic events.

— Read more in Dominik Wodarz and Natalia L. Komarova, “Dependence of the Firearm-Related Homicide Rate on Gun Availability: A Mathematical Analysis,” PLoS ONE 8, no. 7(26 july 2013): e71606 (doi:10.1371/journal.pone.0071606)