Gun Buy Back Programs Probably Don’t Work

When I was still a criminology professor, I remember one day while out getting groceries receiving a cold call from a police department interested in collaborating. They asked if I could provide evidence to support their cities plan to implement sex offender residence restrictions. While taking the call I was walking past a stand for the DARE program.

A bit of inside pool for my criminology friends, but for others these are programs that have clearly been shown to not be effective. Sex offender restrictions have no evidence they reduce crimes, and DARE has very good evidence it does not work (and some mild evidence it causes iatrogenic effects – i.e. causes increased drug use among teenagers exposed to the program).

This isn’t a critique of the PD who called me – academics just don’t do a great job of getting the word out. (And maybe we can’t effectively, maybe PDs need to have inhouse people do something like the American Society of Evidence Based Policing course.)

One of the programs that is similar in terms of being popular (but sparse on evidence supporting it) are gun buy back programs. Despite little evidence that they are effective, cities still continue to support these programs. Both Durham and Raleigh recently implemented buy backs for example.


What is a gun buy back program? Police departments encourage people to turn in guns – no questions asked – and they get back money/giftcards for the firearms (often in the range of $50 to $200). The logic behind such programs is that by turning in firearms it prevents them from being used in subsequent crimes (or suicides). No questions asked is to encourage individuals who have even used the guns in a criminal manner to not be deterred from turning in the weapons.

There are not any meta-analyses of these programs, but the closest thing to it, a multi-city study by Ferrazares et al. (2021), analyzing over 300 gun buy backs does not find macro, city level evidence of reduced gun crimes subsequent to buy back programs. While one can cherry pick individual studies that have some evidence of efficacy (Braga & Wintemute, 2013; Phillips et al., 2013), the way these programs are typically run in the US they are probably not effective at reducing gun crime.

Lets go back to first principles – if we 100% knew a gun would be used in the commission of a crime, then “buying” that gun would likely be worth it. (You could say an inelastic criminal will find or maybe even purchase a new gun with the reward, Mullin (2001), so that purchase does not prevent any future crimes, but I am ignoring that here.)

We do not know that for sure any gun will be used in the commission of a crime – but lets try to put some guesstimates on the probability that it will be used in a crime. There are actually more guns in the US than there are people. But lets go with a low end total of 300 million guns (Braga & Wintemute, 2013). There are around half a million crimes committed with a firearm each year (Planty et al., 2013). So that gives us 500,000/300,000,000 ~ 1/600. So I would guess if you randomly confiscated 600 guns in the US, you would prevent 1 firearm crime.

This has things that may underestimate (one gun can be involved in multiple crimes, still the expected number of crimes prevented is the same), and others that overestimate (more guns, fewer violent crimes, and replacement as mentioned earlier). But I think that this estimate is ballpark reasonable – so lets say 500-1000 guns to reduce 1 firearm crime. If we are giving out $200 gift cards per weapon returned, that means we need to drop $100k to $200k to prevent one firearm crime.

Note I am saying one firearm crime (not homicide), if we were talking about preventing one homicide with $200k, that is probably worth it. That is not a real great return on investment though for the more general firearm crimes, which have costs to society typically in the lower 5 digit range.

Gun buy backs have a few things going against them though even in this calculation. First, the guns returned are not a random sample of guns. They tend to be older, long guns, and often not working (Kuhn et al., 2021). It is very likely the probability those specific guns would be used in the commission of a crime is smaller than 1/600. Second is just the pure scope of the programs, they are often just around a few hundred firearms turned in for any particular city. This is just too small a number to reasonably tell whether they are effective (and what makes the Australian case so different).

Gun buy backs are popular, and plausibly may be “worth it”. (If encouraging working hand guns (Braga & Wintemute, 2013) and the dollar rewards are more like $25-$50 the program is more palatable in my mind in terms of at least potentially being worth it from a cost/benefit perspective.) But with the way most of these studies are conducted, they are hopeless to identify any meaningful macro level crime reductions (at the city level, would need to be more like 20 times larger in scope to notice reductions relative to typical background variation). So I think more proven strategies, such as focussed deterrence or focusing on chronic offenders, are likely better investments for cities/police departments to make instead of gun buy backs.

References

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