Posts Tagged ‘Violence’

Mother Jones Again. Actually Texas State

Wednesday, May 22nd, 2013

Mother Jones, not content with having running one of the more bogus studies on mass shootings (for which they boast about winning an award from Ithaca College), is crowing again about a new study out of Texas State. They claim that the study shows that mass shooting are rising, that available guns are the reason and that civilians never stop shootings.

It’s too bad they didn’t read the paper too carefully. Because it supports none of those conclusions.

  • The Texas State study covers only 84 incidents. Their “trend” is that about half of these incident happened in the last two years of the study. That is, again, an awfully small number to be drawing conclusions from.
  • The data are based on Lexis/Nexus searches. That is not nearly as thorough as James Alan Fox‘s use of FBI crime stats and may measure media coverage more than actual events. They seem to have been reasonably thorough but they confirm their data from … other compilations.
  • Their analysis only covers the years 2000-2010. This conveniently leaves out 2011 (which had few incidents) and the entirety of the 80′s and 90′s, when crime rates were nearly twice what they are now. The word for this is “cherry picking”. Consider what their narrow year range means. If the next decade has fewer incidents, the “trend” becomes a spike. Had you done a similar study covering the years 1990-2000, using MJ’s graph, you would have concluded that mass shootings were rising then. But this would have been followed by five years with very few active shooter events. Look at Mother Jones’ graph again. You can see that mass shootings fell dramatically in the early 2000′s, then spiked up again. That looks like noise in a flat trend over a 30-year baseline. But when you analyze it the way the Blair study does, it looks like a trend. You know what this reminds me of? The bad version of global warming skepticism. Global warming “skeptics” will often show temperature graphs that start in 1998 (an unusually warm year) and go the present to claim that there is no global warming. But if you look at the data for the last century, the long-term trend becomes readily apparent. As James Alan Fox has show, the long-term trend is flat. What Mother Jones has done is jump on a study that really wasn’t intended to look at long-term trends and claim it confirms long-term trends.
  • Mother Jones’ says: “The unprecedented spike in these shootings came during the same four-year period, from 2009-12, that saw a wave of nearly 100 state laws making it easier to obtain, carry, and conceal firearms.” They ignore that the wave of gun law liberalization began in the 90′s, before the time span of this study.
  • MJ also notes that only three of the 84 attacks were stopped by the victims using guns. Ignored in their smugness is that a) that’s three times what Mother Jones earlier claimed over a much longer time baseline; b) the number of incidents stopped by the victims was actually 16. Only three used guns.; c) at least 1/3 of the incident happened in schools, were guns are forbidden.
  • So, yeah. They’re still playing with tiny numbers and tiny ranges of data to draw unsupportable conclusions. To be fair, the authors of the study are a bit more circumspect in their analysis, which is focused on training for law enforcement in dealing with active shooter situations. But Mother Jones never feels under any compulsion to question their conclusions.

    (H/T: Christopher Mason)

    Update: You might wonder why I’m on about this subject. The reason is that I think almost any analysis of mass shootings is deliberately misleading. Over the last twenty years, gun homicides have declined 40% (PDF) and gun violence by 70%. This is the real data. This is what we should be paying attention to. By diverting our attention to these horrific mass killings, Mother Jones and their ilk are focusing on about one one thousandth of the problem of gun violence because that’s the only way they can make it seem that we are in imminent danger.

    The thing is, Mother Jones does acknowledge the decline in violence in other contexts, such as claiming that the crackdown on lead has been responsible for the decline in violence. So when it suits them, they’ll freely acknowledge that violent crime has plunged. But when it comes to gun control, they pick a tiny sliver of gun violence to try to pretend that it’s not. And the tell, as I noted before, is that in their gun-control articles, they do not acknowledge the overall decline of violence.

    Using a fact when it suits your purposes and ignoring it when it doesn’t is pretty much the definition of hackery.

    Mathematical Malpractice: Spree Killings Again

    Monday, December 17th, 2012

    This analysis, which claims that the US has more school spree killings than 36 nations combined, is getting a lot of play. It shouldn’t. It is extremely bad mathematical malpractice.

    The basic reason it is mathematical malpractice is the same reason the Mother Jones study was: it is difficult to analyze extremely rare events. When you narrow your investigation to events that happen maybe once a decade and are compiled haphazardly, you are simply going to be dominated by small number statistics and selection bias. You can therefore use those numbers to say, basically, anything you want.

    Let’s break down just how bad the numbers are being twisted here.

    1) The sample ends in 2009. That excludes the recent spate of knife attacks in Chinese schools that have left 21 dead. If you did this analysis a week ago, you would have had to drop China from the right column.

    2) The sample excludes acts of terror or war. But if Islamists shoot up a school because they don’t want girls to read, are those kids any less dead? If a drone strike misses its targets and kills a classroom, are those kids less dead? Why must we exclude the Beslan attack that left 186 kids dead?

    3) The sample excludes single homicides, which amount to 302 deaths in the United States over the time involved and God knows how many in other countries. So you are literally excluding 90% of the problem and focusing just on a tiny subset of killings.

    4) Comparing us to 36 other countries is ridiculous when some of those countries are places like Bosnia-Herzegovina (population 4 million). We have more population, period, then 30 of the countries on that list combined. Also included in that list of countries are England, Scotland and Northern Ireland, which are, technically speaking, not countries.

    5) The problem of small number statistics can be best illustrated by playing with the data a bit. If I include the knife attacks and move China into the left column, suddenly China has more violent deaths than 30 other countries. If I move Germany onto the left side, suddenly they have more spree killings than a bunch of other countries. If I define the sample in the 1990′s, suddenly Australia dominates the statistics. You simple can not draw conclusions from samples that are that sensitive to single events.

    6) Combining points 4 and 5, if you look at spree killing rates rather than the deliberate mathematical malpractice of comparing absolute numbers, the situation is very different. In 2009, the Winnenden shooting killed 15. Scaled up to the population of the United States, that would be the equivalent of 60 people dead, more than the worst year the United States has ever had. In 1996, 35 people were kill in Port Arthur, Australia. Scaled up to the US population, that would almost equal 500 dead. It is an event that is seared into the memories of Australians. My point is not that these countries are worse than we are. My point is that these are rare and horrible events and you can manipulate the numbers to prove anything you want.

    7) The biggest thing missing here is a sense of time. Is the rate of school killings going up or down? The answer, of course, is down. Check out chart one at Ezra Klein’s blog that shows that the rate of assault death has fallen by over half since 1970. Check out the NCES page I link above which shows a significant decline in on-campus homicides, from 40/year in the 90′s to 30/year in the 00′s. That decline is a hundred more kids running in the sunshine. The NCES data, based on a complete sample of over 600 incidents, is useful. This …. isn’t.

    I’m not trying to downplay the horror that unfolded on Friday. However, I don’t think any debate can proceed unless we have a good grasp of the problem we are trying to solve. Far too many children are murdered in school in this country — that was as true on Thursday as it is today. But to be useful, the debate needs to be on honest terms. Committing mathematical malpractrice by deceptively comparing the United States to 36 other countries as though there something to be learned from that is not an honest debate and is likely to produce a panicky and ill-considered response.