The divide between voting preferences of Americans who own guns and those who do not quadrupled between 1976 and 2012, according to a study published this month in Social Science Quarterly.

University of Kansas researchers determined gun ownership not only predicts a voter’s choice of candidate, but has become one of the most reliable metrics in determining a person’s political preference over the last three decades.

“Gun owners are developing a powerful political identity that rivals other groups’ characteristics in its ability to predict voting behavior,” the study reads. “Indeed, possessing a ﬁrearm increased the likelihood of voting for a Republican candidate, and the gap between gun owners’ and non-gun owners’ voting preferences expanded with every election. We therefore establish a powerful, previously ignored, determinant of vote choice and observe its impact increasing across elections, reaching a level in 2012 nearly 50 percent higher than in 1972.”

By compiling and analyzing the results of the General Social Survey, researchers determined the gap between owners and non-owners who voted for Republican presidential candidate Richard Nixon in the 1972 general election was just over 7 percent. In 2012, the last year of the survey studied, the gap between the same voter blocks increased to 30.2 percent.

Don Haider-Markel, professor and chair of the Department of Political Science at the University of Kansas was one of four researchers on the study. He told Newsweek on Thursday gun owners’ preference for Republican candidates was “the single most important finding” of the project.

“Indeed, the Second Amendment is sacrosanct and gun ownership is viewed as crucial to protecting constitutional liberties from government encroachment,” Haider-Markel and his team wrote in the study. “We thus assert that gun ownership will be an important predictor of Republican Party candidate choice, independent of other known and powerful determinants.”

Haider-Markel said another study is already in the works — this time measuring voting preferences in congressional races and searching for similar patterns. He predicts gun owners’ allegiance to the Republican party will continue.

“It’s not to say that couldn’t decrease in the next election cycle, or if you had a Democratic candidate for president who was taking a different kind of position on guns, that couldn’t change,” he said. “But it just seems unlikely in the short term that’s going to change.”