I realized something in the aftermath of my foiled-by-ccw not-carjacking. Guns DO have a social utility, but we'll never be able to measure it to rigorous scientific standards. When Mr Thug tried to take my car and stopped at the sight of my carry gun, no report was generated. The cops didnt show up, and the bad guy definitely didn't run to a local PD station to report he had the kitten scared out of him whilst breaking the law.
I'm theorizing dozens of times throughout America bad guys and gals are deterred by their intended victim producing a firearm at a choice moment. There won't be any paper trail to follow, however, because unless someone actually gets shot the police don't get called. No police report means no paper which can be used in a verifiable study or survey.
Sadly, when the bad guys attack unarmed victims there's all kinds of documented proof, which means the opposition always has stats while we don't.