Some interesting research on gun violence

Posted by AzBlueMeanie:

Brad Plumer at Ezra Klein's Wonkblog has an interesting analysis of the question Why are mass shootings becoming more common?

Of the 12 deadliest shootings in U.S. history, six have taken place since 2007. (The Newton school shooting will likely rank second on that list.) Mass killings appear to be on the upswing — even as other types of homicides and violent crimes are becoming less frequent.

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For much of the 20th century there were, on average, a handful of mass killings per decade. But that number spiked in 1980, and kept rising thereafter. In the United States, there have now been at least 62 mass shootings in the past three decades, with 24 in the last seven years alone. This has happened even as the nation’s overall violent crime and homicide rates have been dropping.

So what explains the rise in mass killings? 

One theory is that mass murders (usually defined as murders with four or more victims over a short time period) are somehow contagious. Back in 1999, four public health researchers published a famous study titled “Media and Mass Homicides” in the Archives of Suicide Research. They studied a series of mass homicides in Australia, New Zealand, and Britain in the 1980s and 1990s and found that different incidents appeared to be influenced by each other in a number of ways, often spanning many years and across continents.

The idea that one spree killing might inspire another has given rise to plenty of articles and papers about whether the press should be more conscientious in the way it reports on these events. Giving a murderer too much publicity might be a bad idea.

A great deal of research, however, suggests that behavioral scientists just don’t have a strong grasp on what drives mass killings and violent rampages, or why they’ve surged in recent decades.

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Mental illness is one likely factor — a survey by Mother Jones found that at least 38 of the 61 mass shooters in the past three decades “displayed signs of mental health problems prior to the killings.” Yet the studies above note that researchers still have a ways to go before they understand the exact connection between the two.

And what about the availability of guns as a factor? Researchers have found a connection between guns and homicide — more guns tend to lead to more murder. And guns will obviously make any mass attack far deadlier. Note that there was also an attack on 22 students in a Chinese elementary school on Friday. But there was a key difference: The man only had a knife, and there were zero fatalities.

Again, though, overall gun violence in the United States has been declining in recent years while mass shootings and killings appear to have become more commonplace. It’s not entirely clear why that is. And it’s an increasingly important question.

There was an attempt to answer this question shortly after the Tragedy in Tucson in January 2011. Richard Florida, Senior Editor at The Atlantic and Director of the Martin Prosperity Institute at the University of Toronto, posted this report The Geography of Gun Deaths:

The map [below] charts firearm deaths for the 50 states plus the District of Columbia. Note that these figures include accidental shootings, suicides, even acts of self-defense, as well as crimes. As of 2007, 10.2 out of every 100,000 people were killed by firearms across the United States, but that rate varies dramatically from state to state. In Hawaii, at the low end, it was 2.6 per 100,000; in New York and New Jersey it was 5.0 and 5.2 respectively. At the high end, 21.7 out of every 100,000 residents of the District of Columbia were killed by guns, 20.2 in Louisiana, 18.5 in Mississippi, and 17.8 in Alaska. Arizona ranked eighth nationally, with 15.1 deaths per 100,000.


With these data in hand, I decided to look at the factors associated with gun deaths at the state level. With the help of my colleague Charlotta Mellander, we charted the statistical correlations between firearm deaths and a variety of psychological, economic, social, and political characteristics of states. As usual, I point out that correlation does not imply causation, but simply points to associations between variables.

Gun ViolenceEDIT-thumb-600x600-40178

Let's start by looking at factors that are sometimes assumed to be associated with gun violence but statistically are not.

It is commonly assumed that mental illness or stress levels trigger gun violence. But that's not borne out at the state level. [Mass shooters are an exception.] We found no statistical association between gun deaths and mental illness or stress levels. We also found no association between gun violence and the proportion of neurotic personalities.

Images of drug-crazed gunmen are a commonplace: Guns and drug abuse are presumed to go together. But, again, that was not the case in our state-level analysis. We found no association between illegal drug use and death from gun violence at the state level.

Some might think gun violence would be higher in states with higher levels of unemployment and higher levels of inequality. But, again, we found no evidence of any such association with either of these variables.

So what are the factors that are associated with firearm deaths at the state level?

Poverty is one. The correlation between death by gun and poverty at the state level is .59.

An economy dominated by working class jobs is another. Having a high percentage of working class jobs is closely associated with firearm deaths (.55).

And, not surprisingly, firearm-related deaths are positively correlated with the rates of high school students that carry weapons on school property (.54).

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Firearm deaths were far less likely to occur in states with higher levels of college graduates (-.64) and more creative class jobs (-.52).

Gun deaths were also less likely in states with higher levels of economic development (with a correlation of -.32 to economic output) and higher levels of happiness and well-being (-.41).

And for all the terrifying talk about violence-prone immigrants, states with more immigrants have lower levels of gun-related deaths (the correlation between the two being -.34).

And what about gun control? … Might tighter gun control laws make a difference? Our analysis suggests that they do.


The map overlays the map of firearm deaths above with gun control restrictions by state. It highlights states which have one of three gun control restrictions in place – assault weapons' bans, trigger locks, or safe storage requirements.

Firearm deaths are significantly lower in states with stricter gun control legislation. Though the sample sizes are small, we find substantial negative correlations between firearm deaths and states that ban assault weapons (-.45), require trigger locks (-.42), and mandate safe storage requirements for guns (-.48).

While the causes of individual acts of mass violence always differ, our analysis shows fatal gun violence is less likely to occur in richer states with more post-industrial knowledge economies, higher levels of college graduates, and tighter gun laws. Factors like drug use, stress levels, and mental illness are much less significant than might be assumed.

The fact that the mass shooting in Newtown, Connecticut occured in a "rich state with more of a post-industrial knowledge economy, a high level of college graduates, and tight gun laws" does not negate these general findings. Mass shooters are a different breed from other gun related violence.

0 responses to “Some interesting research on gun violence

  1. Divorce is more common killers are much more likely to come from fractured homes. More wealth easier to buy a gun.