by Ozy on (Jan 30, 2013) (republished with permission)
So, what number are we talking about? 2.5 million. That's the often quoted number of annual DGU, usually presented as is, without qualifications or error bars leading one to believe that this is an indication of lives saved, injuries avoided, or at the very least violent crimes prevented due to the presence of a gun by the potential victim.
This is a huge number. An unbelievably huge number...
... this will mostly be an examination of work by others and an attempt to figure out whether any of the numbers make sense, and whether they can or should be used to inform policy.
The studies I will refer to are the following:
Kleck 1995
Hemenway 1997
Kleck 1997 (Kleck responds to criticism of the NSDS)
Cook 1998
I'll try to summarize the main arguments of each study as best as possible, but for more details, the links are provided above.
The 2.5 million DGU number comes from Kleck 95, and it is based on 56 positive responses (weighted to 66) from a pool of 5000 surveyed. The DGU number comes from taking 66/5000 and multiplying by the number of adults in the US at the time (~200 million). Two common critiques to this methodology come from a consideration of 'false positives', and using 'external validation' to compare against other crime statistics.
...
Kleck's response is twofold, that the incidences he's measuring may not reflect typical crimes (e.g. trespassing or other non-violent crime or threat), and DGU incidences may be significantly under-reported because of illegal gun use, or other illegal activities. So, what the heck is he actually measuring?
I mean, when we're talking about trying to assess the positive social utility of DGU, scaring kids off your property by flashing a shotgun doesn't automatically go in the 'plus' category in my mind. Indeed, if you look at Table 3 in Kleck 95, you find that almost 50% of the DGU he measured involved no actual threat posed to the defender. WTF?
In fact, the primary theme that Kleck 97 uses to answer Hemenway's objections is that there is vast under-reporting of DGU because they are usually used illegally and/or in conjunction with illegal activity on the part of the defender.
…Continue reading A closer look at DGU numbers
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