The Risk of Mass Shootings

The shootings at Sandy Hook Elementary last week were horrific.  There is no denying that fact.  Twenty-eight innocent people were murdered.  If that weren't shocking enough, most of them were children.  This event and its aftermath are emotionally charged.  While we need to honor and respect that emotion, we also need to understand that it can cloud our judgment. The emotions we feel compel us to find a reason for disaster and implement a solution quickly.  Many times we are drawn to what appears to be the obvious cause of the disaster and attack it.  The trouble with this approach is that the obvious cause is not always the root cause.  I think we're heading in that direction in the Sandy Hook shootings and mass shootings in general.

Almost immediately, the Sandy Hook shooting generated pleas to avoid politicizing it in the context of of gun control.  The pleas fell on deaf ears and we are focusing our attention on the obvious cause of the deaths at Sandy Hook: Guns.  A friend of mine on Facebook shared an article entitled Twelve Facts About Guns and Mass Shooting in the United States.  There are twelve facts in the article, but they are framed with much rhetoric and I got the feeling that they weren't really used to paint an accurate view.  I decided to collect my own data and see what they said.

As an information risk guy, my next step was to look at the risk we're concerned with.  You need an asset and a threat acting against it to have a risk.  In this instance the asset is human life.  The threat actor is a gun-wielding attacker intent on killing as many people as possible.  I'd have to assign a dollar value to a human life to do this risk assessment correctly, but I think assigning a value to human life would cause more distracting arguments.  I don't know how I'd assign a value to my kid's life.  Let's just agree that the value of human life is significant and focus on the probability of the threat actor causing a loss.

Our threat actor is a gun wielding attacker.  We need to figure out how often we can expect he will successfully take a life.  According to the FBI [8], 15,399 people were murdered in 2009 and 67% of the murders involved a firearm [5].  That gives us a total of 10,317 people murdered with firearms in 2009.   As points of reference, 33,883 people died in highway accidents [2] and 89,241 victims reported being raped in 2009 [6].  The United States population in 2009 was 307,006,550 [10].  United States residents are roughly twice as likely to die in a highway accident than be murdered by a firearm.  They are roughly five times more likely to be raped than murdered with a firearm.  The point I'm trying to make here is that the probability of being murdered with a firearm is relatively low compared to other forms of violent crime.

Next let's look at historical trends in firearm ownership and murder rates.

You can see the data table here

Looking at this data, I have made the following observations:

  1. The Gun Owner rate has been trending down over the past 20 years1
  2. Murders rates have trended down over the past 20 years
  3. Mass murder events are rare as they happen between 0 to 6 times annually, the mean and median values are both 2, and the mode is 1

Assuming the intent of gun control law is to reduce the number of gun owners and gun violence, it seems to be working.  Also, the loss event frequency is low. I don't believe that  gun control law focused on reducing the rate of gun ownership is the root cause of the mass shooting risk based on this data.

Assuming society wants to reduce violent crime rates as a whole,  it seems we'd be more effective focusing on reducing the rate of  highway fatalities and rape.  Those risks are much more significant in terms of frequency.  As a reminder, frequency is only half the equation.  Asset value is the other half and I am not about to start arguing about the value of human life.  The value of human life is significant.  Decide what it means to you and apply these frequency statistics to get a feel for your risk.

As I researched this blog post, I found a lot of interesting data.  I tried jamming it all into one post and it just became ponderous.  I'll have a couple follow on posts to discuss the other data I found.  The next post will focus around the data posted in the Mother Jones article [1].


1 I concede that the gun ownership is self-reported and could include some bias, but it's the best data I could find.  Let me know if you have other data to review with  a note in the Comments.



[1]  M. Follman, G. Aronsen, and D. Pan, “A Guide to Mass Shootings in America,” Mother Jones, 15-Dec-2012. [Online]. Available: [Accessed: 19-Dec-2012].

[2]  “Data and Statistics,” National Transportation Safety Board. [Online]. Available: [Accessed: 17-Dec-2012].

[3]  “FARS Encyclopedia,” National Highway Traffic Safety Administration. [Online]. Available: [Accessed: 17-Dec-2012].

[4]  “Gun Ownership Statistics & Demographics,” Statistic Brain, 20-Jul-2012. [Online]. Available: [Accessed: 17-Dec-2012].

[5]  “Murder Weapon Statistics,” Statistic Brain, 13-Aug-2012. [Online]. Available: [Accessed: 17-Dec-2012].

[6]  “Rape Statistics,” Statistic Brain, 26-Jul-2012. [Online]. Available: [Accessed: 17-Dec-2012].

[7]  L. Saad, “Self-Reported Gun Ownership in U.S. Is Highest Since 1993,” Gallup, 26-Oct-2011. [Online]. Available: [Accessed: 17-Dec-2012].

[8]  “Table 1 - Crime in the United States by Volume and Rate per 100,000 Inhabitants 1992-2011,” FBI. [Online]. Available: [Accessed: 17-Dec-2012].

[9]  E. Klein, “Twelve facts about guns and mass shootings in the United States,” Washington Post, 14-Dec-2012. [Online]. Available: [Accessed: 19-Dec-2012].

[10]  “USA QuickFacts from the US Census Bureau,” United States Census Bureau, 10-Dec-2012. [Online]. Available: [Accessed: 18-Dec-2012].