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?
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:
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.
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:
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.
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.
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.
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.
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":
The second image contains some scatter plots of the data, state by state:
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.
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.
Edit Referencing CBC story Mass shootings in the U.S.: Guns, glory, broken dreams A new study sheds light on why mass shootings in the U.S. are 'an exceptionally American problem', Aug 25, 2015. This article states that Adam Lankford recently presented at the American Sociological Association's conference the results along the lines of the following:
Using data compiled by the New York City Police Department in its 2012 report on active shooting incidents in the U.S. and around the world, as well as data from a 2014 FBI report, Lankford determined that the U.S. had 90 mass shooting incidents during that time frame.
...
America's gun culture and the widespread availability of firearms, contributes to the country's mass shooting problem, the study says. It found that American mass shooters were more likely to arm themselves with multiple weapons, though they killed fewer people than shooters in other countries.
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While Lankford's study suggested a strong link between the civilian firearm ownership rate and the number of public mass shooters in the United States, he said there could be other factors that make the U.S. especially prone to public mass shooting incidents.
America puts more pressure on its citizens to succeed professionally and financially than other countries, Lankford discusses in his study, and when Americans have bad experiences at work or school and fail to achieve their goals, they are more likely to respond with acts of violence.
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Then there's also the idolization of fame, which appears uniquely American, according to Lankford. Increasingly in the U.S., especially among young people, becoming famous is considered the ultimate form of success.
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"Unfortunately, due to some combination of strains, mental illness and American idolization of fame, some mass shooters succumb to terrible delusions of grandeur, and seek fame and glory through killing," his study says. They realize that the only way they will become a household name is by killing innocent people.
Which is all to say, according to the article and the underlying study the exceptionally high number of American gun massacres is linked to:
That is to say: Gun control would reduce the prevalence, but I think it is fair to say that one should be cautious of using gun control as a solution because the underlying demand for mass murders in America will remain (as created by mental illness, cultural expectations, and desire for fame).
