Scholars Richard Florida and Charlotta Mellander recently studied state-to-state variation in gun homicide levels. They found that "[f]irearm deaths are significantly lower in states with stricter gun control legislation." This is backed up by research on local gun control efforts and cross-border gun violence.

Josh Marshall asks for counter-evidence:

There have been a number of ‘studies’ I’ve seen purporting to substantiate the claim that widespread gun ownership will actually reduce violence. But the ones I’ve seen either come from disgraced amateurs or think tank hacks with zero peer review. Are there any methodologically sound, peer-reviewed studies which show anything like this?