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I have seen numerous arguments about gun control, in the sense of laws restricting gun ownership or possession, and whether widespread gun possession affects crime rates, and each side is happy to pull out studies that are favorable to their side. I really haven't felt I could trust any of them.

I hope this isn't too much of a hot potato, but are there any serious scientific studies available? Or at least reasonably unbiased?

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Gun control is a large umbrella that encompasses a large number of policies. Do you really really any type of gun control or are you referring to a particular policy (prohibition, registry, etc.)? –  Borror0 Mar 18 '11 at 2:57
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This question is not very good. What about the effects of removing gun control? Without both sides of the equation it's impossible to remove any cultural effects for example. –  Sklivvz Mar 19 '11 at 11:14
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I believe your question is asking if governmental gun control laws are effective. The government itself, however, is the largest perpetrator of [violence][1]. If gun control laws are needed then the the government itself should be the first target for such restrictions. [1]: edfriendly.blogspot.com/2011/02/… –  Muro Mar 22 '11 at 21:11
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In regards to Mark's study that claims that gun control laws were the reasons for reduced homicide rates starting in the 90s. Freakonomics covered this topic and statistically showed that it was in fact the legalization of abortion that resulted in not only the lower homicide rates but also the reduced crime rates. Most aborted fetuses came from what would have been lower income families, which tend to commit higher rates of crime. It is no coincidence that the reductions began 18 years after abortion became legal. –  Dunk Mar 22 '11 at 22:04
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@Benjol: We're not talking about government-imposed abortions. The usual reason a woman would have an abortion is that she doesn't feel ready to raise a child, for some reason, and has become pregnant. This means that abortion reduces the number of badly raised children, and apparently therefore the crime rate later on. This has nothing to do with any sort of agenda or social control. (I refuse to get involved in a pro- or anti-abortion argument here.) –  David Thornley May 23 '11 at 14:12

5 Answers 5

I don’t know how well a single case-study can be generalised, or applied in a different cultural setting. But since jozzas’ answer on the Australian gun control act exclusively relies on a paper that completely misrepresents the evidence here’s another stab at it:

Background

In 1996, after a mass shooting with an illegally purchased but legally available semi-automatic weapon in Port Arthur, Tasmania that killed 35 people and wounded 23, Australia enacted the National Firearms Agreement (NFA), a strict ban on semi-automatic weapons and stricter requirements for acquiring a weapon permit. They also enacted a compulsory gun buyback scheme taking effect immediately which resulted in 600,000 guns being bought back from the state, at a cost of 500 million AUS$. The government levied a 1% addition in income tax for one year to finance this.

Data & evidence

The following gives a broad overview over a huge mass of data. I tried my hardest to represent the data fairly; however, by necessity I leave out quite a lot (otherwise I’d have to publish a paper). Most of the missing data and justifications can be found in Leigh & Neill [2] which gives a truly excellent run-down of the evidence, along with a careful explanation and justification of the statistical methods used, and a comprehensive explanation of the limitations of the data. In fact, this latter point makes the paper stand out particularly.

  • Massacres. In the 18 years prior to the enactment of the NFA, there had been 13 massacres in Australia involving guns (defined as killing ≥ 4 people). In the years since, there have been none. However, while such large-scale killings are obviously tragic events they contribute relatively little to the overall rates of deaths by guns.

  • Murder rate. Australia has generally had low levels of violent crime even before the ban. Furthermore, there’s been a steady decline in the number of firearm-related deaths since the early 1980s [1, 2], in particular, there was a 47% decrease between 1991 and 2000. This was accompanied by a similar decrease in non-firearm related murders.

    On the other hand, there was a clear acceleration of the reduction after the NFA was enacted, but [2] found that this reduction falls short of statistical significance.

  • Suicide rate. What they managed to show, though, was that the NFA buyback contributed strongly and significantly to a reduction in suicides. To ensure that they weren’t just looking at a reduction over time which started before the NFA, they compared across states and correlated reduction with number of guns bought back by the state, and find that more gun buyback by the state results in more reduction in suicide with a statistically significant trend (R2 = 0.7685, p-value = 0.004% – this is a very robust statistic that cannot be explained away by any other factors that the authors examined). The gun buyback led to a reduction by 1.9 per 100,000 for each 3.500 withdrawn guns per 100.000 individuals (95% CI), which is a 74% reduction.

    This state-dependent trend and its correlation is shown here:

    change in firearm suicide versus gun buyback

  • Compensation. Both murder and suicide rates declined globally, that is, reductions in gun death weren’t increased by use of other weapons. However, in the first few years after the NFA, non-gun suicides were briefly raised, continuing a prior trend, before dropping as well. No such trend exists for homicides.

  • Cost. The gun buyback cost 500 million AUS$. On the other hand, [2] estimates that the 200 annual deaths thus prevented correspond to an economic saving of 500 million AUS$ per year. This would correspond to a 7 billion AUS$ cost saving.

    Could this money have spent differently to get a similar (or better) reduction in gun-related deaths? I couldn’t find any data analysing this. However, the buyback was essentially a one-off cost so amortised over time no ongoing intervention could have a better cost-benefit relation.

Significance

As mentioned, the robust data analysis shows a marked reduction in suicide rates. [2] goes into more detail to improve the robustness of the analysis by doing subsampling and trying (unsuccessfully) to explain the reduction with other variables.

Lee & Suardi [3] have argued that no such reduction exists for homicide rates because the time series data doesn’t show a “structural break”. That may be so ([2] didn’t find a statistically significant reduction for homicide rates either). However, [2] notes that such structural breaks cannot be assumed to exist due to the large number of factors influencing death rates.

Baker & McPhedran [4] claim that even the suicide rate reduction is not related to the NFA buyback. However, [2] notes that this paper is deeply flawed since it wouldn’t infer significance even if homicide rates had been negative in the years after 2004, and that the authors of [4] “should know better”.

Overall, the NFA and buyback were correlated with a significant reduction in firearms related deaths, and no balancing increase in non-firearms related deaths.

Putting things into perspective

Is this evidence convincing? Yes: It is the best evidence we have, and while statistically flawed methods find no effect, correcting statistical mistakes invariably finds a significant reduction. And in fact, it is the best evidence we could hope for, because it is the kind of signal we would expect to get if we knew that there were a real effect: no sharp break but a steady decline. In fact, in the words of the authors of [2],

from the perspective of 1996, it would have been difficult to imagine more compelling future evidence of a beneficial effect of the law.


Notable references

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Can you double check the link that you have from the "semi-automatic weapon" text? Right now it is going to the page for AR-10 which doesn't seem appropriate as the actual article says that an AR-15 and FN FAL were used. There are some nuances here as the AR-15 was capable of fully-automatic for 3 round burst fire depending on the model. Or perhaps just link to the relevant semi-automatic link? –  rjzii Dec 18 '12 at 21:15
    
@Rob Ah, thanks. I just copied the description from one of the news articles (can’t be bothered to double-check which one it was now) and you’re right, it’s sufficient just to link to the general description. –  Konrad Rudolph Dec 18 '12 at 21:48
    
… and as always I’d appreciate if downvotes were accompanied by feedback. –  Konrad Rudolph Dec 18 '12 at 22:26
    
Not sure who the down vote came from, wasn't me other than the link issue I thought the answer was good. :) –  rjzii Dec 19 '12 at 4:03
    
I would argue that the only thing this shows is that a massive gun confiscation program was effective. That's quite a different thing from the laws being effective. –  Jasmine Jul 23 at 18:53

From: Gun Control Effects on Crime and Murder

Very much like the larger scope of the entire gun control debate, it is of no surprise that both opposing factions will reach a stalemate in regarding gun control and its actual effects on crime and murder. However, it is important to note that arguments and debate on the subject are not the main reason as to being able to determinately claim fact to one or the other, but it is the discrepancy in the statistics and facts themselves that lend to dispute.

Furthermore the author goes on to state some statistics:

In general, it has been reported that 60% to 70% of all homicides involve firearms. Out of this firearms, about 80% involved handguns. Since the implementations of more restrictions and regulations involving the purchases, possession, or carrying of handguns have been more explicitly stressed since the 1970s and 1980s, there has been a general decline of firearm related violent related crimes, particularly homicides. From the early 1990s to turn of the century, this decline has been at a steady average at about 10% each year, with a total decline of about 50%. Such statistical reports will provide for factual evidence extensively showing how crime can be reduced with pro gun control implementations. Not only do these numbers prove a positive effect about gun control, but it is a drastic and impressive one. Another report showed that there are about 6.3 million violent crimes committed in 1999. Violent crimes including rape or sexual assault, robber, and assault were considered for this statistic. Out of those crimes, just over 500,000 involved the use of firearms, which is about 8% of the total estimation of violent crimes. This statistic essentially shows that firearms are not necessarily properly correlated with their use during violent crimes, and therefore, extensive gun control laws deem to be excessive and unfair to those citizens legally allowed to own and use them. An example of how stricter gun control laws did not aid in lowering crime rates is Washington D.C. In 1976, D.C. adopted what was to be considered one of the few extremely restrictive gun control policies in the country. The murder rate since the time of new gun control policy rose 134%. Yet another example is New York City, which also implemented similarly stringent gun laws as D.C. had similar results. In the early 1970s, about 19 % of homicides involved pistols, and shortly after the new laws were in place, this number rose to about 50%. Furthermore, the restriction of firearms allowed for only 28,000 lawfully possessed or acquired firearms, yet law enforcement estimations had the number at 1.3 million illegal handguns in the city. Conversely, states with fewer restrictions such as New Hampshire and Vermont, have proven to the safest of all the states, with Vermont ranking in at 49th in crime and 47th in murders.

I emphasized a few important points.

The conclusion I draw is that there are situations where gun control appears to directly save lives, but in other situations gun control has almost no effect. Though the crack epidemic may have simply outweighed the effects of gun control. Another reason that these laws may have been ineffective is that guns can be purchased at gun shows in other states, which may render gun control laws in nearby areas mostly useless.

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The first half of the quote seems to be a cum hoc ergo propter hoc fallacy (it is rarely a good idea to assume causal connection between two societal trends based on a single example). The other half could easily be cherry-picked data; the methodology is not declared, and you will probably find a few examples to for prejudice, given a large enough data set. –  Tgr Mar 20 '11 at 11:03
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The second part: it is important to note that US census 2009 has NY city with 8.3 million people, while Vermont's total state population is .6 million. Population densities correlate strongly with crime. –  horatio Mar 22 '11 at 14:48
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"The conclusion I draw is that there are situations where gun control appears to directly save lives, but in other situations gun control has almost no effect." One could say exactly the same for penicillin, which has saved millions of lives!? –  Sklivvz Dec 15 '12 at 1:52
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This is a nice statistic. en.wikipedia.org/wiki/… Compare for an example Switzerland(guns at home) and Germany(strict gun laws). Switzerland has 10 times higher rate of gun related homicides than Germany (with similar culture and economic status) –  Stefan Dec 17 '12 at 15:37
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Is this US? Global? Otherwise? The post doesn't really show the geographic coverage. –  gerrit Dec 18 '12 at 19:21

Australia, in response to a killing spree, outlawed automatic weapons and placed severe restrictions on other types of weapons in 1996. The effects of gun control in Australia have been widely studied, but this meta-analysis shows no significant outcome on murder or suicide rates:

  • Wang-Sheng Lee, Sandy Suardi, The Australian Firearms Buyback and Its Effect on Gun Deaths Melbourne Institute Working Paper Series wp2008n17, Melbourne Institute of Applied Economic and Social Research, The University of Melbourne, 2008.

    The 1996-97 National Firearms Agreement (NFA) in Australia introduced strict gun laws, primarily as a reaction to the mass shooting in Port Arthur, Tasmania in 1996, where 35 people were killed. Despite the fact that several researchers using the same data have examined the impact of the NFA on firearm deaths, a consensus does not appear to have been reached. In this paper, we re-analyze the same data on firearm deaths used in previous research, using tests for unknown structural breaks as a means to identifying impacts of the NFA. The results of these tests suggest that the NFA did not have any large effects on reducing firearm homicide or suicide rates.

It should also be noted that Australia has always had comparatively very low rates of gun crime.

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I don't think "meta-analysis" is the right term for this paper. It isn't a systematic review and they didn't combine data sets. Perhaps "re-analysis" is a better summary, as they analysed the data with a different (apparently more appropriate?) statistical model. –  Oddthinking Dec 15 '12 at 1:48
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This answer puzzles me. Before 1996, there were multiple killing sprees in Australia but none since. This seems like a massive improvement. “no significant outcome on murder or suicide rates” is therefore cherry-picking evidence. –  Konrad Rudolph Dec 17 '12 at 9:52
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… The “no significant outcome on … suicide rates” furthermore appears to be false. In particular, the graph in the article showing a strong linear correlation between buyback and lowered suicide rates is damning. Furthermore, the Lee & Suardi paper has been criticised for its flawed analysis of homicide rate. –  Konrad Rudolph Dec 17 '12 at 10:18
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@Brendan 13 times in the 18 years prior. So yes, a very sharp decline indeed. –  Konrad Rudolph Dec 18 '12 at 9:45
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@jozzas Whether or not there was a decline prior to the ban is irrelevant to what I said. The graph I was referring to shows a direct response in decline to the buyback. And no, plotting the graph over another timeline would not look similar. And there’s no cherry-picking because the graph doesn’t show what you claim it shows: it doesn’t show a general downward trend over time (look at the x axis!), it shows the direct effect of gun buyback. But referring to the general decline you mentioned, you failed to mention that after 1996 there was a statistically significant increase in decline. –  Konrad Rudolph Dec 18 '12 at 9:49

There is some evidence from state to state comparisons that gun control laws and gun ownership show some relationship to deaths from firearm use

For many observers outside the USA it seems obvious that the lax US attitude to gun control is a major contributor to the high rate of death from gun use in the USA (the USA is an outlier in death rates at least among developed countries). But these international comparisons are always going to be subject to many confounding factors. However, different states inside the US have very different rules about firearm ownership and control so this might offer better, less confounded an more relevant, evidence for whether tighter control is useful in the US context.

A recent piece of research in the journal JAMA Internal Medicine analyses the internal state by state legislation and its relationship to death rates. The study concludes:

A higher number of firearm laws in a state are associated with a lower rate of firearm fatalities in the state, overall and for suicides and homicides individually. As our study could not determine cause-and-effect relationships, further studies are necessary to define the nature of this association.

Two visualizations of their data are worth repeating. The first is a map of death rates and legislative "strength":

enter image description here

The second image contains some scatter plots of the data, state by state:

enter image description here

It is also worth noting the limitations of the study. In the authors own words (i've highlighted some of the key issues):

Our study has limitations. First, the legislative strength score, which tallies a single point per law, has not been validated. Neither has the weighted Brady scoring system, and we are unaware of any such scoring systems that have been validated. Our results, which divided states into quartiles of legislative strength, were essentially the same with either of these scoring systems. Second, we examined only deaths by firearms, not nonfatal firearm injuries; fatality was our primary outcome. Approximately 2.6 nonfatal firearm injuries are treated for every fatal firearm injury. Third, we were unable to control for the enforcement of firearm laws or the exploitation of loopholes, which may vary between states. Fourth, although we adjusted for many state-based factors associated with firearm fatalities, there may be additional factors not considered in our model that are relevant (eg, city laws and police enforcement). However, we included nonfirearm suicides and nonfirearm homicides in some of our analyses to control for the potential role of additional factors. We found little evidence of substitution—rates of firearm-related deaths were not correlated with rates of nonfirearm violent death in the multivariable model. Fifth, although we found that states with more legislation have lower fatality rates, ie, are “safer” states, in a cross-sectional ecological study we could not determine if the greater number of laws were the reason for the reduced fatality rates. The association could have been confounded by firearm ownership rates or other unaccounted factors.

So, in conclusion, there appears to be some relationship between tighter gun control and gun deaths (for both suicides and homicides). But the quality of evidence required to demonstrate causality is not yet available.

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Another thing they didn't control for (not sure if they included it in "enforcement" caveat) - how many homicides were attributed to legally owned vs illegally owned weapons. Both AZ and NM - looking at the end of the list#2 - are plausibly likely to have tons of the latter, due to narcotics related issues. –  DVK Apr 1 '13 at 5:05
    
@DVK It would be very difficult to control for illegal versus legally owned weapons. State laws are not uniform. They vary widely. In fact, legality varies at a city and even borough level. As a resident of Arizona, and having been raised in New Mexico, I confess that I was non-plussed upon reading your supposition that we are more illegal weapon- and narcotic-afflicted than other border states e.g. Texas or California, or other states in general. Also, the population of New Mexico is tiny, compared to the other states of the USA. –  Feral Oink Apr 27 '13 at 13:49

According to the BBC article Missouri gun murders 'rose after law repeal',

Reporting soon in the Journal of Urban Health, the researchers will say that the [gun control law's] repeal resulted in an immediate spike in gun violence and murders.

The study links the abandonment of the background check to an additional 60 or so murders occurring per year in Missouri between 2008 and 2012.

"Coincident exactly with the policy change, there was an immediate upward trajectory to the homicide rates in Missouri," said Prof Daniel Webster, director of the Johns Hopkins Center for Gun Policy and Research.

It looks like the paper cited has sensible controls for the conclusions:

"That upward trajectory did not happen with homicides that did not involve guns; it did not occur to any neighbouring state; the national trend was doing the opposite – it was trending downward; and it was not specific to one or two localities – it was, for the most part, state-wide," he told BBC News.

The team said it took account of changes that occurred in policing levels and incarceration rates, trends in burglaries, and statistically controlled for other possible confounding factors such as shifts in unemployment and poverty.

According to the BBC the underlying study is to-be reported in the Journal of Urban Health. If vetted, the study would be compelling evidence that the absence of gun control laws correlates with higher gun violence and murders.

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Thanks @GlenTheUdderboat –  Brian M. Hunt Feb 17 at 19:16
    
-1. The only way you can see the paper's conrtols as "sensible" is if you desperately want to believe the author's desired conclusion. As I noted in this answer, he cherry-picked a state that had an atypically rising murder rate BEFORE the gun control law changed; AND failed to note the curial fact that the rise rate actually SLOWED after the law passed in that state. –  DVK Feb 22 at 20:13
    
@DVK: That's really useful information (though the manner of your presentation could be a bit less accusatory ;)). I believe you have the reputation to edit, and as I am sure you can do it better than I can I would be grateful if you could add your reservations to this answer. Whether convincing or not, I think it's a worthwhile piece to have on this page – since there is a decent chance others will cite it at some point if it is not here already. If you are comfortable with it, I think the best approach would be add in the reservations about the paper. Does that make sense? –  Brian M. Hunt Feb 23 at 1:13

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