Saturday, December 22, 2012

Did the Assault Weapons Ban Work?

Did the Assault Weapons Ban Work?

As noted in this article, the Sandy Hook Elementary School shooting in Newtown, Connecticut has brought calls to reinstate an assault weapons ban like the one that expired in 2004. Following is an excerpt of a round table discussion of the shooting on the December 16th edition of This Week With George Stephanopoulos:

WILL: In 1996, a man went into a gym class in Scotland, killed 16 5- and 6-year-olds and the teacher. A few years ago in Norway, a young -- deranged young man killed, what, 69 people on an island, mostly teenagers. Connecticut has among the toughest gun laws in this country. Didn't help. Scotland and Norway have very tough gun laws. Didn't help. So...

STEPHANOPOULOS: Didn't stop, but it does lessen the occasion of violence, doesn't it?

WILL: Yeah, why don't...

EDWARDS: And, George, since Columbine, there have been 181 of these school shootings.

WILL: We did -- remember, we did -- we did have a ban -- we did have a ban on assault weapons. When we put the ban in place, these incidents did not really decline in a measurable way. And when we took it off, they didn't increase in a measurable way.

Hence, George Will is saying that the ban on assault weapons did not have a measurable effect on these mass-shootings. On the December 17th edition of The PBS Newshour, David Kopel, a professor at the University of Denver, was more explicit, saying the following:

Well, I think we can look at what happened when she had her 10-year in the past. The Congress, when it enacted that ban, also ordered that a formal study be done of the results of it.

The study was performed by the Urban Institute, a very well-respected, somewhat left-leaning think tank in Washington, D.C., and the Urban Institute reported that it had no effect on homicide rates. There was no statistically significant benefit in terms of saving lives.

Kopel's statement that the study had reached such a definitive conclusion sounded a little surprising. Looking online, I found the Urban Institute study titled Impact Evaluation of the Public Safety and Recreational Firearms Use Protection Act of 1994 - Final Report. The overview of the study concludes as follows:

At best, the assault weapons ban can have only a limited effect on total gun murders, because the banned weapons and magazines were never involved in more than a modest fraction of all gun murders. Our best estimate is that the ban contributed to a 6.7 percent decrease in total gun murders between 1994 and 1995, beyond what would have been expected in view of ongoing crime, demographic, and economic trends. However, with only one year of post-ban data, we cannot rule out the possibility that this decrease reflects chance year-to-year variation rather than a true effect of the ban. Nor can we rule out effects of other features of the 1994 Crime Act or a host of state and local initiatives that took place simultaneously. Further, any short-run preventive effect observable at this time may ebb in the near future as the stock of grandfathered assault weapons and legal substitute guns leaks to secondary markets, then increase as the stock of large-capacity magazines gradually dwindles.

We were unable to detect any reduction to date in two types of gun murders that are thought to be closely associated with assault weapons, those with multiple victims in a single incident and those producing multiple bullet wounds per victim. We did find a reduction in killings of police officers since mid-1995. However, the available data are partial and preliminary, and the trends may have been influenced by law enforcement agency policies regarding bullet-proof vests.

The following pages explain these findings in more detail, and recommend future research to update and refine our results at this early post-ban stage.

This sounds very different from Kopel's definitive "no statistically significant benefit in terms of saving lives". Yes, they were "unable to detect any reduction to date in two types of gun murders that are thought to be closely associated with assault weapons" but they did detect a "6.7 percent decrease in total gun murders between 1994 and 1995" and a "reduction in killings of police officers since mid-1995". It is important to note that this study was published on March 13, 1997, just over two years after the ban took affect on September 13, 1994. Hence, the study itself recommends "future research to update and refine our results at this early post-ban stage".

In fact, two additional studies that were done are referenced at this link. Like the Urban Institute study, key authors were Christopher S. Koper and Jeffrey A. Roth. The latter of the two is titled An Updated Assessment of the Federal Assault Weapons Ban: Impacts on Gun Markets and Gun Violence, 1994-2003 and was published in June 2004. Following is an excerpt from its first chapter titled "Impacts of the Federal Assault Weapons Ban, 1994-2003: Key Findings and Conclusions":

The Ban’s Success in Reducing Criminal Use of the Banned Guns and Magazines Has Been Mixed

• Following implementation of the ban, the share of gun crimes involving AWs [assault weapons] declined by 17% to 72% across the localities examined for this study (Baltimore, Miami, Milwaukee, Boston, St. Louis, and Anchorage), based on data covering all or portions of the 1995-2003 post-ban period. This is consistent with patterns found in national data on guns recovered by police and reported to ATF.

• The decline in the use of AWs has been due primarily to a reduction in the use of assault pistols (APs), which are used in crime more commonly than assault rifles (ARs). There has not been a clear decline in the use of ARs, though assessments are complicated by the rarity of crimes with these weapons and by substitution of post-ban rifles that are very similar to the banned AR models.

• However, the decline in AW use was offset throughout at least the late 1990s by steady or rising use of other guns equipped with LCMs [large capacity magazines] in jurisdictions studied (Baltimore, Milwaukee, Louisville, and Anchorage). The failure to reduce LCM use has likely been due to the immense stock of exempted pre-ban magazines, which has been enhanced by recent imports.

It is Premature to Make Definitive Assessments of the Ban’s Impact on Gun Crime

• Because the ban has not yet reduced the use of LCMs in crime, we cannot clearly credit the ban with any of the nation’s recent drop in gun violence. However, the ban’s exemption of millions of pre-ban AWs and LCMs ensured that the effects of the law would occur only gradually. Those effects are still unfolding and may not be fully felt for several years into the future, particularly if foreign, pre-ban LCMs continue to be imported into the U.S. in large numbers.

Hence, the study states that gun crimes involving AWs [assault weapons] did decline, primarily due to a reduction in the use of APs [assault pistols]. However, this decline was offset by steady or rising use of other guns equipped with LCMs [large capacity magazines]. The study concludes that "the ban’s exemption of millions of pre-ban AWs and LCMs ensured that the effects of the law would occur only gradually". Once again, this sounds very much different that Kopel's statement that the assault weapon ban provided "no statistically significant benefit in terms of saving lives".

This points to a problem with interviews on news shows, even excellent shows like the PBS Newshour. It is very easy to make many types of erroneous statements with little risk of having the errors exposed, at least not in real time. Even though there may be one or more experts with opposing views, none of them will have all of the facts of all studies at their fingertips. It is therefore easy to slip in various erroneous numbers or conclusions with little risk of being contradicted. This suggests that it might be useful to have similar interviews online where each statement could subjected to some minimal fact-checking before the conversation continues. In any case, it shows that such statements should be treated simply as possibilities unless and until they can be verified.

Note: There is a discussion of this post at this link.

Did the Assault Weapons Ban Work? (Part 2).

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About Me

I became interested in U.S. budget and economic matters back in 1992, the first time that I remember the debt becoming a major issue in a presidential election. Along with this blog, I have a website on the subject at http://www.econdataus.com/budget.html. I have blogged further about my motivations for creating this blog and website at this link. Recently, I've been working on replicating studies such as the analysis at this link.

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