The better question is how many violent crimes are thwarted because of lawful use of a firearm in self-defense.
Or even thwarted just because of the presence of a firearm.
I once drove off an intruder who had actually entered my house with nothing more than a stern loud voice and a very powerful flashlight in his eyes. OTOH without my right hand on the grip of my concealed pistol, I would not have been able to confront him at all.