Congressional Research Service claims that Mass Public Shootings have been increasing, but it fails to provide evidence that this increase is statistically significant

5 Aug , 2015  

Mass Public Shootings 1999 to 2013

The Congressional Research Service (CRS) has just released a new report titled: CRS Mass Murder with Firearms Incidents and Victims 1999-2013.  USA Today’s headline provides a typical reaction: “Report: Mass public shootings on rise.”  While the report points to increases in the number of shooting incidents over this period of time, the CRS does not discuss whether any of these results are statistically significant.  Indeed, if one looks at the period of time that the title of their paper refers, there is no statistically significant increase in the number of incidents or the number of people killed and/or injured.  In fact, the changes per capita are not even close to being statistically significant and the changes are very small.  For the number of incidents per 10 million people, the change is not only statistically insignificant, it implies that there were 0.142 incidents per 10 million in 1999 and this rose to 0.154 in 2013.  To put it differently, that is only a 0.57% increase per year.

Regression on Mass Public Shooting incidents per 10s of million

While the report’s title refers to the period from 1999 to 2013, the CRS also provides data going back to 1970.

Regression on Mass Public Shooting incidents Graph 1970 2013

Previous work by the CPRC has shown that there was no statistically significant increase in the death rate from attacks since 1977 where mass public shootings were defined as 2 or more people killed.  We have requested the CRS data for the years prior to 1999, but we have yet to receive it.  But even if the CRS data is correct, it seems doubtful that there has been a statistically significant increase in the rate of attacks or deaths from them since at least the early 1980s, particularly if the very low rate of mass public shootings in 2014 are included.

The other regression results for mass public shootings over the 1999 to 2013 period are as follows (in both cases t-statistic on the change in deaths or injuries per year is less than 1.

Regression on Mass Public Shooting deaths or injuries per 10s of million


4 Responses

  1. gunnut says:

    James Alan Fox:

    “There’s no solid trend. (…) Basically, there is no rise. There are some years that are bad, some that are not so bad. No matter how you cut it, there’s no epidemic. This report should calm the fears that many people have that these numbers are out of control.”

    http://reason.com/blog/2015/08/03/mass-shootings-study

  2. […] of Mayor Bloomberg and his media allies to whip up fears about such events; Lott went right to work to make sure that we all understood that any increase in mass shootings were “statistically […]

  3. […] Thor is online now   Quote Quick Reply post #4529 of 4529 (permalink) Old Today, 03:53 PM Thor Member     Join Date: Oct 2011 Posts: 6,518 Re: America has a problem with gun insanity Congressional Research Service claims that Mass Public Shootings have been increasing, but it fails … […]

  4. Martin says:

    Is there an update to this to include 2014-2017?

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