More naive Leftist research

The authors quoted below enter the wise caveat that "The findings can’t prove that banning Large Capacity Magazines  reduces mass shootings and deaths".  Yet many people quoting the findings will ignore that caveat and write as if banning Large Capacity Magazines DOES reduce mass shootings and deaths.  So I think I should expand on what lies behind the caveat.

Basically, the study repeats an error that occurs with nauseous frequency in epidemiological research -- despite the fact that the report below appeared in a prestigious medical journal.

The failure was that the authors did not ask WHY people fell into the category being studied.  In this case they did not ask WHY some states ban LCGs and some don't.  America has frequent gun-based massacres so there is always vigorous agitation to restrict gun ownership and use in some way. And restricting magazine size is a popular policy of that ilk.

So the key question is WHY the anti-gun agitation gets results in some states and not in others.  To understand that we have to look at how gun restrictions are viewed.  And I don't think it is drawing too long a bow to suggest that a key variable in that is how dangerous it is perceived to be to be unarmed. If gun attacks are perceived as highly likely, gun use is going to be much more extensively protected than in places where the threat of violent incursions is seen as low. 

So in some states we expect to see a high threat to the citizen from illegal gun users and resultant loose gun laws to enable the citizen to defend himself.  And where the gun laws are loose, access to LCGs is unlikely to be restricted.  So LCGs are more likely to be found and used in high crime areas.  And that, roughly, is what the research found.

As a psychologist I feel a need to add that how dangerous an area is and how dangerous it is perceived to be may not be perfectly aligned.  A major factor is the politics of the area.  Leftists seem to walk around for most of their lives in a mental world that is well divorced from reality. So in areas where they predominate, areas may be seen as much safer than they are

So the causal arrow may point to the dangerous area as being the cause of the excess deaths rather than which magazine is used


Large-Capacity Magazine Bans Linked With Fewer Mass Shootings, Deaths

Jennifer Abbasi

In a recent study, US states without large-capacity magazine (LCM) bans had more high-fatality mass shootings and higher death rates during these assaults. The findings, recently detailed in the American Journal of Public Health, could support banning these efficient ammunition-feeding devices.

Military-style “assault weapons” get a lot of attention from policy makers and the public, but most high-fatality mass shootings are perpetrated with semiautomatic handguns. Large-capacity magazines arm all types of semiautomatic firearms, not just assault weapons, so banning the devices could have a greater effect on such incidents, the study authors said.

Proposals to restrict LCMs are being considered to combat gun violence. However, there isn’t a lot of evidence on the effects of LCM bans.

The Design

The researchers analyzed associations between high-fatality mass shootings and state and federal LCM bans starting in 1990—when the first state (New Jersey) began restricting LCM ownership—through 2017. During that time, 8 additional states and Washington, DC, enacted bans. The time frame also included the now-expired 1994 Federal Assault Weapons Ban that for a decade made it illegal to produce, sell, transfer, or own new LCMs.

The researchers looked at the state and federal bans both together and separately. Based on the federal rule, they defined LCMs as magazines that hold more than 10 rounds of ammunition. They considered high-fatality mass shootings those with 6 or more deaths not including the shooter. To account for other differences among states, they controlled for 10 variables, including population density, education, unemployment rate, and a proxy for percentage of households with firearms.

What We’ve Learned

There were 69 high-fatality mass shootings during the study period. Forty-four of them involved LCMs and 16 didn’t. The researchers couldn’t determine if LCMs were involved in the remaining 9 shootings.

The attacks were more common in states without LCM bans. Forty-nine occurred in such states, whereas just 20 happened in states with bans.

More people died in shootings that involved LCMs: 11.8 on average, compared with 7.3 in attacks without the magazines. Nonban states also saw more deaths on average per attack: 10.9, compared with 8.2 in states with bans.

The percentage of shooters who used LCMs was 81% in states without bans but only 55% in states with bans.

Only 12 of the shootings and 89 of the deaths occurred during the 10-year federal ban. But over the following 13 years, there were 48 such shootings and 527 deaths.

The first full year after the federal ban expired, 8 high-fatality mass shootings occurred in states with LCM bans, while 39 happened in those without them.

The Caveats

There wasn’t information about LCMs for 13% of the incidents.

The researchers acknowledged that the magnitude of the associations may have been overestimated because of the (relatively) small number of shootings that met the study’s criteria for high-fatality mass shootings.

Knowing which mass shootings with fewer than 6 deaths involved LCMs would have been valuable, but most of these data either are not documented or are not readily available, the researchers told JAMA.

What the Researchers Say

The findings can’t prove that banning LCMs reduces mass shootings and deaths, but the main conclusions didn’t change when other explanatory variables were factored in. This indicates that “differences across states in these dimensions were not the reason for the strong association between LCM bans and lower rates of high-fatality mass shooting deaths,” said the study’s senior author, David Hemenway, PhD, of the Harvard T.H. Chan School of Public Health in Boston.

According to Hemenway, LCMs allow the shooter to fire more shots without reloading—and reloading gives time for someone to intervene and for potential victims to get out of harm’s way. Possibly for this reason, states that have enacted LCM bans have had fewer high-fatality mass shooting incidents, fewer victims killed per incident, and far fewer high-fatality mass shooting fatalities per capita.

“Overall, the theory behind reducing the availability of LCMs to reduce the number of victims in mass shootings makes sense, and our empirical results suggest that LCM bans have saved lives,” he said.

However, the authors pointed out that the bans don’t immediately eliminate all LCMs. Some are grandfathered in, while others are illegally imported from places where they’re still legal.

 JAMA. Published online December 18, 2019. doi:https://doi.org/10.1001/jama.2019.20457