Just living near a place where guns are easily for sale is associated with a greater risk of being killed by an intimate partner. GaiaConventi/Shutterstock

Whether a person ends up being murdered by their partner could come down to the distance to the nearest gun dealer. The higher the number of dealerships in an urban county, the more people killing their spouse or lover, although the same relationship doesn't apply in rural areas. This is for America of course – few other nations have enough gun dealerships to conduct similar analysis, and most have much lower rates of intimate partner homicide.

While traumatized by the news of yet more mass shootings, it is easy to forget that the number of people killed in these events is far exceeded by shootings of family members, particularly intimate partners. It's well established the presence of a gun in the home raises the risk one resident will kill another, either as murder or by accident. Indeed, according to one study, a gun in a house is 22 times more likely to be used to kill a resident of the home than an intruder.

Dr Richard Stansfield and Dr Daniel Semenza of Rutgers University looked deeper by comparing the number of intimate partner homicides with the number of gun dealers in every county of 16 US states.

In rural counties, they found no correlation, but in their study published in the journal Preventative Medicine they report the urban relationship is strong. "This study showed this robust association regardless of whether the victims were male or female or how old the victims were," Dr Stansfield said in a statement.

"If there is greater access to legal guns, it could make it easier for someone to purchase a gun in the throes of an argument, before there is time to cool off," Dr Semenza added. The authors acknowledge the work doesn't rule out some other explanation for the correlation. Perhaps gun dealers locate their shops in places where people are more prone to violence, but the authors say their work adds to a growing body of evidence that access is key.

The authors hope to refine their research by including the exact distance from the murder site to the nearest gun shop, rather than relying on county-level data. To make the case stronger, it would be useful to know how many of the guns used in these cases were acquired legally, but this information is harder to obtain.

The reason for the rural/urban divide hasn't been tested, but the authors suggest guns are so common in rural American houses that someone contemplating violence seldom needs to leave home to acquire one.

The authors didn't test for a correlation with shops selling violent video games, as there is an abundance of previous evidence showing gaming doesn't increase violence. Not that it will stop politicians trying to point the blame that way.