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In an effort to determine the relationship between gun ownership and gun deaths, a researcher from the Boston University School of Public Health looked at 30 years of data in all 50 states. His determination? For each percentage point increase in the number of households with guns, there was a 0.9 percent increase in the rate of firearm homicides. And that wasn't the only factor linked to an increase in gun deaths.

Motivated by the December 2012 massacre at Sandy Hook Elementary, the researcher, Dr. Michael Siegel, gathered and analyzed data detailing a variety of social factors to determine which might correlate to increased gun deaths. The nearly one-to-one relationship between the percentage of homes with a gun and the number of gun-involved murders is remarkable. (It has been peer reviewed.)

What's additionally interesting are those other factors also showing a statistically significant link to firearm killing rates.

Variable Increase in variable Increase in firearm homicides
Household gun ownership 1% 0.9%
Income inequality 0.01* 4.6%
Black population 1% 5.2%
Violent crime rate 1 crime in 1,000 population 4.8%
Non-violent crime rate 1 crime in 1,000 population 0.8%

* As measured by the Gini coefficient.

In an email to The Atlantic Wire, Siegel noted that the household gun ownership rate used a rather macabre proxy, in lieu of state-by-state data: the percentage of suicides committed with a firearm. "The reason we had to use this proxy," he explained, "is that state-specific household firearm ownership data are not available except for 3 years: 2001, 2002, and 2004." Measuring the proxy against the data from those years, however, it demonstrates similar results.

That allowed Siegel to compile data on estimated per-household gun ownership for each state over the three decade time period. He provided to The Atlantic Wire a table of data illustrating the shift in ownership for each time period, as well as the overall rates over the 30 years. In each graph below, the darker the color, the higher the percentage of households that own guns.

Switch to: Entire period | 1981-1990 | 1991-2000 | 2001-2010

The dip in ownership over time also corresponds to the overall decline in murders in America.

While Siegel explained to us that the additional factors listed in the table above were "very important and that identifying and understanding them is critical from a public health standpoint," his focus was on ownership. The paper describes what higher gun ownership in one state might indicate about its murders.

All other factors being equal, our model would predict that if the [household proxy data] in Mississippi were 57.7% (the average for all states) instead of 76.8% (the highest of all states), its firearm homicide rate would be 17% lower.

Fewer guns; fewer gun-related murders. Which could be good news. After all, Siegel's research also notes a drop from 60.6 percent of households owning guns in 1981 to 51.7 percent in 2010.

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