Does gun control reduce violence? No. But if you ask the Hillary supporting Center for American Progress (CAP) they’ll roll out their special report saying that it does. The report, as an aside, has been referenced by The New York Times. That’s a bad start. Robert Verbruggen at The American Conservative, explains how the report references the “Gun Violence Index.” The index is basically a measure of gun deaths. But two-thirds of gun deaths are suicides, not violence. Stricter state guns laws do not correlate with less gun violence. Verbruggen explains:
We can see the importance of this second point in CAP’s own data. Most strikingly, the report’s central claim—that states with stricter gun laws have less gun violence—does not hold for homicide, which is what most people think of when they hear “gun violence.” Not that most readers could tell that from the report: the finding is relegated to a footnote, and even there the authors fail to note that the correlation is far too weak to be considered statistically significant.
(Technically speaking, it’s 0.13, with 50 observations, one for each state. That translates to a “p-value” of 0.37, far above the traditional 0.05 cutoff. If you generated the data at random, there would be more than a one-in-three chance of getting a correlation this strong.)
None of this is necessarily to deny that weak gun laws or high gun ownership—CAP’s report makes no attempt to distinguish between the two*—can have bad consequences. They do seem to correlate with suicide rates, as well as some specific types of homicide, including police and intimate-partner violence. Even when it comes to overall homicide rates, some more advanced studies (though far from all) argue there’s a correlation there once the data have been adjusted to account for differences in demographics and culture.
Of course, such adjustments are crucial if we are trying to discover causation, and not mere correlation. But CAP’s analysis makes no attempt to perform them. And even if we could definitively say that strict gun laws reduce violence, the analysis would say nothing about which gun laws in particular help, because they’re all compressed into a single scale.