On the state level, mental illness and stress levels don't play a role. Poverty and gun control policies do.
Last night's horror in Aurora, Colorado, once again confronts America with the senseless tragedy of gun violence. The debate over this country's relationship to guns will start all over again, and this time, in the middle of a presidential campaign.
The map below, by my colleague Zara Matheson at the Martin Prosperity Institute, charts the geography of gun violence across the 50 states plus the District of Columbia, based on data from the Centers for Disease Control and Prevention [PDF]. The data (from 2008, the most recent year available) include accidental shootings, suicides, even acts of self-defense, as well as crimes.
There were 10.3 deaths by firearms per 100,000 people in Colorado in 2008, exactly the same as the national average. Gun deaths were highest in Alaska (20.9 per 100,000) and lowest in Hawaii (3.1 per 100,000).
Last year, I took a deeper look at the the factors associated with gun deaths at the state level.
Gun violence and drug abuse are often presumed to go together, but we found no association between illegal drug use and death from gun violence at the state level. While it is commonly assumed that mental illness or stress levels trigger gun violence, we found no association between gun violence and the proportion of neurotic personalities in any given state.
Some might assume 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.
We did find several factors that are associated with firearm deaths at the state level. On the economic front, gun violence was higher in states with lower average incomes. Similarly, gun violence was less likely in states with more college graduates and stronger knowledge-based economies. Gun violence was also higher in states that tend to vote Republican.
In a separate post, I examined the pyschogeography of gun deaths. The classic study of the subject is by Richard Nisbett, a social psychologist at the University of Michigan. In "Violence and Regional Culture," published in American Psychologist in 1993, Nisbett examined the higher rate of violence in the U.S. south. After considering possible explanations having to do with poverty, the legacy of slavery, and even the region's hotter climate, he found a different answer in a cultural vestige of pastoralism: a deep "culture of honor" in which residents place an extraordinary value on personal reputation, family, and property. Threats to these things provoke aggressive reactions, leading to higher rates of murder and domestic violence.
A more recent study by Ryan P. Brown, Lindsey Osterman, and Collin Barnes of the University of Oklahoma, published in Psychological Science in 2009, reinforces Nisbett's findings and suggests that a culture of honor plays a particularly significant role in high school violence. The study found a culture of honor to be significantly associated with two indices of school violence: the percentage of high school students who reported having brought a weapon to school during the past month; and the prevalence of actual school shootings over a 20 year period.
My research also found a correlation between state policies toward guns and gun ownership:
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).