Both sides in the gun debate are misusing academic reports on the impact of the 1994 assault weapons ban, cherry-picking portions out of context to suit their arguments.

Wayne LaPierre, chief executive officer of the National Rifle Association, told a Senate committee that the “ban had no impact on lowering crime.” But the studies cited by LaPierre concluded that effects of the ban were “still unfolding” when it expired in 2004 and that it was “premature to make definitive assessments of the ban’s impact on gun violence.”

Conversely, Sen. Dianne Feinstein, who has introduced a bill to institute a new ban on assault weapons, claimed the 1994 ban “was effective at reducing crime.” That’s not correct either. The study concluded that “we cannot clearly credit the ban with any of the nation’s recent drop in gun violence.”

Both sides in the gun debate are selectively citing from a series of studies that concluded with a 2004 study led by Christopher S. Koper, “An Updated Assessment of the Federal Assault Weapons Ban: Impacts on Gun Markets and Gun Violence, 1994-2003.” That report was the final of three studies of the ban, which was enacted in 1994 as part of the Violent Crime Control and Law Enforcement Act of 1994.

The final report concluded the ban’s success in reducing crimes committed with banned guns was “mixed.” Gun crimes involving assault weapons declined. However, that decline was “offset throughout at least the late 1990s by steady or rising use of other guns equipped with [large-capacity magazines].”

Ultimately, the research concluded that it was “premature to make definitive assessments of the ban’s impact on gun crime,” largely because the law’s grandfathering of millions of pre-ban assault weapons and large-capacity magazines “ensured that the effects of the law would occur only gradually” and were “still unfolding” when the ban expired in 2004.

The Competing Claims

Now both LaPierre and Feinstein are lifting parts of the reports out of context to bolster their arguments for or against a renewed ban.

Testifying before the Senate Judiciary Committee on Jan. 30, LaPierre said of the 1994 ban that “independent studies, including one from the Clinton Justice Department, proved that ban had no impact on lowering crime.” The testimony LaPierre submitted to the committee cited the first of the three major studies on the ban — this one by Koper and Jeffrey A. Roth in 1997 — in a footnote to support that claim.

The 1997 study said its analysis “failed to produce evidence of a post-ban reduction in the average number of gunshot wounds per case or in the proportion of cases involving multiple wounds.” But that’s not the same as saying the ban had “no impact.” The authors noted that the study was “constrained” to findings of short-term effects, “which are not necessarily a reliable guide to long-term effects.”

And most fundamentally, the authors wrote, “because the banned guns and magazines were never used in more than a fraction of all gun murders, even the maximum theoretically achievable preventive effect of the ban on gun murders is almost certainly too small to detect statistically with only one year of post-ban crime data.” The two later major studies of the ban included more years of analysis and concluded with an “updated assessment” that was published in 2004.

Feinstein, meanwhile, put out a press release touting her proposed legislation, the Assault Weapons Ban of 2013, which claims that “the 1994 Assault Weapons Ban was effective at reducing crime.”

Specifically, Feinstein’s press release cites a Justice Department study of the assault weapons ban that, it says, “found that it was responsible for a 6.7 percent decrease in total gun murders, holding all other factors equal” (citing the 1997 study) and that “the use of assault weapons in crime declined by more than two-thirds by about nine years after 1994 Assault Weapons Ban took effect” (citing the 2004 study). We briefly addressed this issue in a previous article.

Both sides are cherry-picking from the studies. Here’s a fuller context of what the third and final study actually concluded:

Koper, 2004: Although the ban has been successful in reducing crimes with AWs [Assault Weapons], any benefits from this reduction are likely to have been outweighed by steady or rising use of non-banned semiautomatics with LCMs [large-capacity magazines], which are used in crime much more frequently than AWs. Therefore, we cannot clearly credit the ban with any of the nation’s recent drop in gun violence. And, indeed, there has been no discernible reduction in the lethality and injuriousness of gun violence, based on indicators like the percentage of gun crimes resulting in death or the share of gunfire incidents resulting in injury, as we might have expected had the ban reduced crimes with both AWs and LCMs. However, the grandfathering provision of the AW-LCM ban guaranteed that the effects of this law would occur only gradually over time. 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. It is thus premature to make definitive assessments of the ban’s impact on gun violence.

In Koper’s Own Words

We were not able to reach Koper directly, but it so happens that he gave a presentation on his findings at a Summit on Reducing Gun Violence in America, held at Johns Hopkins University on Jan. 14 and 15. (His presentation begins at about the 30-minute mark.)

Koper, who is currently an associate professor in the Department of Criminology, Law and Society at George Mason University, provided this summary:

Koper, Jan. 14: What we found in these studies was that the ban had mixed effects in reducing crimes with the banned weaponry due to various exemptions that were written into the law. And as a result, the ban did not appear to effect gun violence during the time it was in effect. But there is some evidence to suggest that it may have modestly reduced shootings had it been in effect for a longer period.

That the law did not have much of an impact on overall gun crime came as little surprise, Koper said. For one, assault weapons were used in only 2 percent of gun crimes before the ban. And second, existing weapons were grandfathered, meaning there were an estimated 1.5 million pre-ban assault weapons and 25 million to 50 million large-capacity magazines still in the U.S.

“So obviously, these grandfathering provisions had major implications for how the effects of the law would unfold over time,” Koper said.

The study found “clear indications that the use of assault weapons in crime did decline after the ban went into effect” and that assault weapons were becoming rarer as the years passed (this is the part of the study Feinstein seized on). But, he said, the reduction in the use of assault weapons was “offset through at least the late 1990s by steady or rising use of other semi-automatics equipped with large-capacity magazines.”

And here is the part that LaPierre highlights:

Koper, Jan 14: In general we found, really, very, very little evidence, almost none, that gun violence was becoming any less lethal or any less injurious during this time frame. So on balance, we concluded that the ban had not had a discernible impact on gun crime during the years it was in effect.

But Koper went on to say that an assault weapons ban “could potentially produce at least a small reduction in shootings” if allowed to remain in place for a longer time frame.

Koper, Jan. 14: The grandfathering provisions in the law meant that the effects of the law would occur only very gradually over time. It seems that those effects were still unfolding when the ban was lifted, and indeed they may not have been fully realized for several more years into the future even if the ban had been extended in 2004. The evidence is too limited for any firm projections, but it does suggest that long term restrictions on these guns and magazines could potentially produce at least a small reduction in shootings.

Other studies, he said, have suggested attacks with semiautomatic guns – particularly those having large magazines – “result in more shots fired, persons hit and wounds inflicted than do attacks with other guns and magazines.” Another study of handgun attacks in Jersey City during the 1990s, he said, “estimated that incidents involving more than 10 shots fired accounted for between 4 and 5 percent of the total gunshot victims in the sample.”

Koper, Jan. 14: So, using that as a very tentative guide, that’s high enough to suggest that eliminating or greatly reducing crimes with these magazines could produce a small reduction in shootings, likely something less than 5 percent. Now we should note that effects of this magnitude could be hard to ever measure in any very definitive way, but they nonetheless could have nontrivial, notable benefits for society. Consider, for example, at our current level of our gun violence, achieving a 1 percent reduction in fatal and non-fatal criminal shootings would prevent approximately 650 shootings annually … And, of course having these sorts of guns, and particularly magazines, less accessible to offenders could make it more difficult for them to commit the sorts of mass shootings that we’ve seen in recent years.”

Koper concluded by saying that “a new ban on large capacity magazines and assault weapons would certainly not be a panacea for gun crime, but it may help to prevent further spread of particularly dangerous weaponry and eventually bring small reductions in some of the most serious and costly gun crimes.”

That kind of guarded language may not make for great sound bites for either side in the gun debate, but it more accurately reflects Koper’s findings and conclusion.

— Robert Farley