<p>A few years back, a study was published by Kleck and Gertz which concluded that each year 2.5 million crimes were prevented by civilians (i.e., not police officers or security guards) with guns - by brandishing them, shooting them, or merely talking about them. This assertion is accepted and repeated by a large group of people. </p>
<p>The obvious flaws in the methodology of the study, as well as its factual conflict with reliable data, are interesting to dig into, but to me, a more fundamental question arises: Have people lost the ability to relate statistical assertions to their own very real lives so as to be able to detect even the most obvious BS?</p>
<p>The specific claim based on the study is this (“DGU” means “defensive gun use”):
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<p>Okay, let’s just mull that over for a minute. 1.3% of all American adults prevented at least one crime - last year - by brandishing, shooting, or referring to a gun. Not only that, but it happens year in and year out. And it’s not the same 1.3% every year - while there’s some overlap, the study results actually suggest that for the most part it’s a new group doin’ it each and every year (222/4799 yields 4.6% over five years, or a new .9% of the population engaging in DGU’s each year).</p>
<p>So, my having been an adult for about forty years, I should personally know a lot of people this has happened to. 40 X .9 = 36%! Of course the population has turned over during that time period with old people dying and new people achieving adulthood, so if it was done just once per lifetime by each defender it’d be closer to 18%. If we pump up the “repeat defender” rate by assuming that there are repeaters from one 5 year time span to another so we don’t have to assume that 18% of all Americans engaged in DGU over that period of time we’re still left with a substantial fraction of the population. I mean, during that time there’s probably a hundred people I’ve known really well - well enough so that if they had prevented an actual crime (and used a gun to do so) I’m confident that I’d know about it. But I don’t. I actually don’t know a single one. I do know that people do prevent crimes, both with and without guns, and I’ve personally participated in crime prevention a couple of times. (I’ve lived in some fairly high-crime areas.) But actual “crime prevented by gun-totin’ civilian”? Absolutely zero first hand experience, zero reliable second hand experience.</p>
<p>So even without digging into the details of the study, it’s not really too hard for me to figure that it really is a remarkable claim, which is inconsistent with my actual real life experience. In short, my BS meter isn’t just twitching - it’s hit the peg. And frankly - that was before I ran the numbers above - I just did that as a reality check. They had me at “2.5 million times a year.”</p>
<p>So why do people just accept a claim like this? I understand believing in UFO’s - it’s inherent in the belief that the ET’s have the ability to prevent detection and proof, etc. - I mean, they’re an advanced civilization, right? And belief in conspiracies (which is necessary to believe the Kleck/Gertz study as well, by the way) similarly relies on a belief that someone is suppressing the “real truth”. But if people were actually preventing crime all the time - 120,000 time per month - we’d actually know about lots and lots of actual such events, involving people we actually know. But we don’t. At best most of us have a “friend of a friend” that we’ve heard about, or read a story in the newspaper (since such events would typically be dramatic and newsworthy) But we don’t actually have anywhere near the reliable personal information we should have if this claim were true. </p>
<p>So why do people believe stuff which doesn’t even fit with their own very real lives?</p>