Of course, perceptions are not always in line with reality, and they are more strongly influenced by recent events than by those that occurred well in the past. Given the widely-publicized and exceptionally dreadful mass shootings in Colorado last summer and in Connecticut last month, it is rather easy to believe that mass murder, particularly those involving firearms, is a growing menace. Yet the growing menace lies more in our fears than in the facts.

In the ongoing public debate over the causes and solutions to mass shootings, the overwhelming consensus is that mass shootings are on the rise. President Obama mentioned recent deadly rampages while releasing his multi-faceted gun reform proposal. And although former President Bill Clinton may have exaggerated in suggesting that half of all mass killings in the United States have occurred since the 2005 expiration of the Federal assault weapon ban, many Americans sense that these incidents have become much more frequent.

Last Saturday night, a 15-year boy allegedly murdered his parents and three siblings at the family home outside of Albuquerque, N.M. Should we add it to the list of recent mass shootings about which all of America is talking? Of course we should, although according to at least one influential news source it shouldnât be a part of the discussion.

To a large extent the notion that mass shootings are trending is based on the often-cited reporting by Mother Jones, an award-winning online news organization. Mother Jones assembled a data tally of ârandomâ mass shootings over the past couple of decades derived from news reports and collective memories of events, and concluded that mass shootings are indeed on the increase.

After much debate over parameters, Mother Jones settled on several criteria for inclusion in its mass shootings database, specifically:



The killings were carried out by a lone shooter. (Except in the case of the Columbine massacre and the Westside Middle School killings, both of which involved two shooters.)



The shootings happened during a single incident and in a public place. (Public, except in the case of a party in Crandon, Wisconsin, and another in Seattle.) Crimes primarily related to armed robbery or gang activity are not included.



The shooter took the lives of at least four people. An FBI crime classification report identifies an individual as a mass murderer-as opposed to a spree killer or a serial killer-if he kills four or more people in a single incident (not including himself), and typically in a single location.



If the shooter died or was hurt from injuries sustained during the incident, he is included in the total victim count. (But we have excluded cases in which there were three fatalities and the shooter also died, per the previous criterion.)



We included six so-called "spree killings"-prominent cases that fit closely with our above criteria for mass murder, but in which the killings occurred in multiple locations over a short period of time.



Not only is Mother Jonesâs decision to disqualify cases based on certain criteria hard to defend, the criteria themselves were not necessarily applied consistently. Mother Jones included the 1993 Chuck E. Cheese robbery/massacre of four people committed by a former employee, but excluded the Brownâs Chicken robbery/massacre of seven victims that occurred the very same year, presumably because two perpetrators were involved in the latter incident or perhaps because these gunmen had no prior connection to the restaurant.

Mother Jones also eliminated massacres involving family members, even though they too can involve large body counts, such as the massacre of 14 relatives and two others by R. Gene Simmons of Russellville, Ark. in 1987. Other massive shootings, like the execution-style slaughter of 13 in a Seattle club in 1983, were ignored because of their relation to gang activity or some criminal enterprise. Particularly mystifying is the decision not to include cases involving multiple perpetrators yet to waive this condition for two school shootings.

Notwithstanding the questionable motive-based selectivity built into the Mother Jones analysis, it seems odd to ignore shootings with large death tolls just because there was more than one shooter or because the shooter was related to his or her victims. These incidents are no less devastating to the families and communities impacted by the crimes.

So how does the Mother Jones report of a rise in mass shootings stand up when considering the full range of cases? Simply put, not very well.

The figure below displays the number of mass shootings -- incidents and victims -- from 1976 through 2010. These reflect all mass shootings in which at least four victims were killed that had been reported to the FBI by local law enforcement authorities as part of the routine collection of crime statistics. Unlike the Mother Jones approach, these data do not exclude cases based on motive, location, or victim-offender relationship. They only exclude incidents in which fewer than four victims (other than the assailant) were killed, murders committed with a weapon other that a firearm, or isolated cases that may have occurred in jurisdictions that did not report homicide data to the FBI. Also, only because of the usual time lag in crime reporting, the figures for 2011 in 2012 are not yet available.

According to these expanded figures, there have been, on average, nearly 20 mass shootings a year in the United States. Most, of course, were nowhere as deadly as the recent massacres in Colorado and Connecticut that have countless Americans believing that a new epidemic is upon us and have encouraged healthy debate concerning causes and solutions. Notwithstanding the awful tragedies of this past year, there has been no upward trend in mass shootings.

What is abundantly clear from the full array of mass shootings, besides the lack of any trend upward or downward, is the largely random variability in the annual counts. There have been several points in time when journalists and other people have speculated about a possible epidemic in response to a flurry of high profile shootings. Yet these speculations have always proven to be incorrect when subsequent years reveal more moderate levels.

The year 1991, for example, saw a man kill 23 people at a cafeteria in Killeen Tex., and a disgruntled graduate student murder five at the University of Iowa, along with other sensationalized incidents. The surge in mass killings was so frightening that a rumor spread around the nation that there would be a mass murder at a college in the Northeast on Halloween. Fortunately, October 31 came and went without anything close to a massacre taking place.

Two years later, in 1993, the nation was shaken by a series of workplace shootings, which encouraged a number of syndicated talk shows to air special programs about âticking time bombs at the office.â Despite the sudden spike in workplace homicide, the incidence of workplace murders actually declined throughout the 1990s.

The only silver lining to the tragedies of 2012 is that they have generated considerable momentum for tackling the root causes of mass murder. Whether the sense of urgency is sustained long enough for change in law or policy to be implement remains to be seen.

And, if changes do occur, how will we know if they have the desired effect? Given the relative rarity of mass murder, a drop can just as easily (and more likely) reflect the downturn that usually and naturally occurs following a spike. The somewhat comforting news should be that in all probability, 2013 will be an improvement over 2012, at least in terms of mass murder, whether we respond proactively or just talk about it.



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