America's horror over mass shootings has led to calls for gun control in much of the US. But it's also had another effect: leading some more conservative-minded Americans to demand less restrictions on guns so they can defend their families.

A new bill in Georgia would have taken the latter approach, allowing adults 21 and older to carry a gun anywhere on a public college or university campus except at dormitories, fraternity and sorority houses, and athletic events. But after facing enormous pressure from the university system to veto the bill, Gov. Nathan Deal blocked the measure on Tuesday.

This will likely upset conservative lawmakers in the state. They believe that if there are going to be shootings in public schools, people should be able to carry firearms and defend themselves. In their view, that's the only way to deter and stop such attacks.

But the evidence suggests Deal made the right call for students' safety: When people have easier access to guns, gun violence is much more likely. Georgia's bill, then, could have put more people in harm's way.

More guns mean more gun deaths

The idea is simple: The prevalence of guns can cause petty arguments and conflicts to escalate into deadly encounters. People of every country get into arguments and fights with friends, family, and peers. But in the US, it's much more likely that someone will get angry during an argument, pull out a gun, and kill someone. (Prosecutors argue this may have happened during a shooting in Northern Arizona State University last year.)

The research overwhelmingly supports this idea: When there are more guns and gun owners, there are far more gun deaths. Studies have found this to be true again and again — for homicides, suicides, domestic violence, and violence against police.

Here's one chart, from a 2007 study by Harvard School of Public Health researchers, showing the correlation between statewide firearm homicide victimization rates and household gun ownership after controlling for robbery rates:

A more recent study from 2013, led by a Boston University School of Public Health researcher, reached similar conclusions: After controlling for multiple variables, the study found that a 1 percent increase in gun ownership correlated with a roughly 0.9 percent rise in the firearm homicide rate at the state level.

This holds up around the world. As Vox's Zack Beauchamp explained, a breakthrough analysis in the 1990s by UC Berkeley's Franklin Zimring and Gordon Hawkins found that the US does not, contrary to the old conventional wisdom, have more crime in general than other Western industrial nations. Instead, the US appears to have more lethal violence — and that's driven in large part by the prevalence of guns.

"A series of specific comparisons of the death rates from property crime and assault in New York City and London show how enormous differences in death risk can be explained even while general patterns are similar," Zimring and Hawkins wrote. "A preference for crimes of personal force and the willingness and ability to use guns in robbery make similar levels of property crime 54 times as deadly in New York City as in London."

These studies aren't the only ones to reach such conclusions. Multiple reviews of the research, including the Harvard Injury Control Research Center's aggregation of the evidence, have consistently found a link between gun ownership and gun deaths after controlling for other factors.

Guns are not the only factor that contribute to violence. (Other factors include, for example, poverty, urbanization, and alcohol consumption.) But when researchers control for other confounding variables, they have found time and time again that America's high levels of gun ownership are a major reason the US is so much worse in terms of gun violence than its developed peers.

That helps explain why the most rigorous reviews of gun policies have concluded that stricter gun laws can reduce gun violence and deaths: A 2016 review of 130 studies in 10 countries, published in Epidemiologic Reviews, found that new legal restrictions on owning and purchasing guns tended to be followed by a drop in gun violence — a strong indicator that restricting access to guns can save lives.

Taking all of this together, the empirical research seems clear: If Georgia or any other state wants to reduce gun violence, the better idea may be to restrict access to guns, not make them easier to carry around.