It appears that the United States is in the throes of an epidemic of mass shootings. Mass murders involving firearms understandably capture public and political attention, overshadowing other types of murder that occur more frequently. (1) After a recent gun-related mass murder in the United States, the father of one victim called for "immediate action" from Congress and the President of the U.S. to pass stricter gun control laws. Additionally, recent media polls reveal that about half of Americans support enactment of stricter gun control laws, and not surprisingly, such support tends to increase as the country bares witness to the horror of these shootings via the media in the aftermath of a mass shooting. (2)
While all agree urgent steps need to be taken to stop mass murders, there remains a serious question as to what degree stricter gun control laws alone can actually decrease mass shootings in the U.S. Although the popular perception is that a strategy of stricter gun control would decrease mass murders, debates about the efficiency of gun control in reducing violent crime remain one of the most widely studied--and widely controversial--disputes in behavioral science literature. Common sense and several studies suggest that greater availability of guns leads to more violent crime. However, convincing empirical evidence that the answers lie in stricter gun control laws alone is actually rather sparse. (3,4) Gary Kleck noted that findings about the efficacy of gun control to reduce violent crime is inconclusive. (5) Similarly, John Moorhouse and Brent Wanner found that state data "provides no evidence that gun control reduces crime rates," even three years after the control policies were implemented. (6) Indeed, John Lott presented analyses showing that the right to carry firearms is linked to decreased crime. (7) It is difficult, then, to draw conclusions about the efficiency of gun control.
Part of the reason for the varied findings on gun control certainly lies in the measurement of variables. Many studies on the efficacy of gun control include all types of gun-related deaths, including suicide and accidental shootings, non-lethal gun violence, murder, and mass killing. Yet, not all of these categories are empirically equivalent. It is certain that these kinds of gun incidences have different moderating and mediating variables that make studying gun control a challenging issue. For instance, there is little reason to believe that the control variables influencing suicide are similar to the controls for mass murder. There are qualitative differences between the different kinds of gun violence, and they should not be conflated in empirical studies on gun control. Perhaps the vast variability in findings can be at least partially attributed to the varying effects of gun control legislation on different kinds of gun violence.
Few studies have specifically teased out the link between gun control legislation and mass murder via shooting. Some of these involve investigating the link between gun control and mass killing outside of the U.S. For example, Chapman, Alpers, Agho, and Jones examined the effects of Australia's semi-automatic weapons, pump-action shot guns, and rifles ban, enacted following a mass killing that claimed thirty-five lives. (8) The authors noted that following the legislation, no incidents of mass killing occurred in Australia. They concluded that gun control was responsible for the decline, even though they are unable to provide evidence of the causal relationship due to the lack of incidences. Using the same framework as Chapman et al., but undertaking different analyses, Jeanine Baker and Samara McPhedran concluded that gun-related suicide was the only parameter likely influenced by the Australian legislation. (9) It should be noted that it is questionable to what degree results in Australia can be generalized to the United States or other countries, and causal inference is limited with quasi-experimental data. A 2016 study examined public mass shootings and firearms in a cross-national study of 171 countries. The study concluded that nations with high firearm ownership are particularly susceptible to mass shootings, noting that the United States had the highest firearm ownership rates and the most mass shootings. However, India has the second highest firearm ownership rate but does not even crack the top five countries in the world for mass shootings. (10)
There are many other potential explanations for a decrease in gun violence as a response to increased gun control. For example, Ik-Whan Kwon and Daniel Baack indicated that socioeconomic and law enforcement factors also play an important role in the reduction of gun fatalities. (11)
Along these lines, using cross-national data from the United Nations and reports from electronically available newspapers and police reports, Frederic Lemieux compared rates of gun deaths in nations identified as having restrictive gun control laws (such as Australia, Norway, Denmark, and Switzerland) and nations identified as having permissive firearm ownership (vis-a-vis handling, storage, and sales oversight), such as the United States. (12) Despite differences in gun deaths between nations, Lemieux found only a weak, negative relationship between gun control and death by firearms. In a small section on mass murder, Lemieux noted that while the United States surpassed all other industrial nations in incidences of mass shootings, rates of victimization tend to be lower (7.01 victims in the United States versus a cumulative average of 10.6 casualties for comparison nations.) Adam Lankford's study suggests the lower American casualty rate per incident is due to routine police training on how to respond to mass shootings.
As already noted, comparing the effects of gun control legislation across nations is a dubious proposition due to a myriad of cultural differences. With so many variables affecting rates of violence, it is difficult--if not impossible--to disentangle all of them sufficiently to attribute observed effects to gun control. Differences in rates of poverty, population density, and law enforcement could all influence rates of gun violence. Indeed, a growing body of research on mass murder within the United States has focused largely on understanding precipitating factors that lead to mass killings; or to the characteristics of the perpetrator. (13) For instance, Hempel, Meloy, and Richards studied a nonrandom sample of thirty adults accused of mass murder and created a general psychological profile of the "typical" offender. (14) Roland Holmes and Stephen Holmes attempt to classify mass murders into various types. (15) James Fox and Jack Levin provide a solid review and analyses of the demographics and typical characteristics of a mass murderer. (16) These studies are informative, but do not aim to provide empirical evidence as to whether gun control is associated with a reduction in mass murder.
Furthermore, while some studies cast doubt on the idea that gun control will decrease the number of incidences of mass murder, it might be possible to use gun legislation to reduce the numbers of victims of mass killings. Considerable social policy has recently centered on the idea of limiting ammunition as a means to reduce the number of victims during mass killing incidents. (17) However, little if any research has been done on the efficacy of this approach in reducing either number of incidences of gun violence or number of victims. This should certainly be an immediate focus for social scientists.
It is challenging to understand the fundamentals of an issue when researchers do not agree on how to define a construct. Most empirical research examining mass murder includes the killing of four or more victims in public or private locations and is not limited to gun crimes. (18) Some studies include gang-related violence, while others do not. There also appears to be debate as to what constitutes a mass murder perpetrated by a firearm. Some reports have curiously excluded cases where shootings have taken place in private homes. (19) Other reports exclude cases in which all the victims were related. As Fox and Levin pointedly noted, such cases still result in carnage. (20)
Thus, this study assesses whether there is a relationship between the strictness of gun control laws and number of mass murder incidents per state. It analyzes the relationship between gun control strictness and incidences of mass murder; as well as rates of victimization from mass murder incidences in the United States. Methods
The data for this study originates from a report on mass murders committed from 2009 to 2015 in the U.S. presented by USA Today. (21) This report featured information about the number of mass murders per state, the number of victims per incidence, and the type of weapons utilized. USA Today employed the Federal Bureau of Investigation's definition of mass murder, which is the killing of four or more individuals, sometimes simultaneously, without a "cooling-off" period. (22) The newspaper collected their data from FBI reports...