It will come as no surprise to those with a passing interest in American politics that Republicans are more likely to own guns than Democrats. But the differences have become much starker in recent years, with gun ownership having become a powerful predictor of political behavior.

In 1973, about 55 percent of Republicans reported having a gun in their household against 45 percent of Democrats, according to the General Social Survey, a biennial poll of American adults.

Gun ownership has declined over the past 40 years — but almost all the decrease has come from Democrats. By 2010, according to the General Social Survey, the gun ownership rate among adults that identified as Democratic had fallen to 22 percent. But it remained at about 50 percent among Republican adults.