I read the other thread about the Brady bunch scoring states on gun control. Well, that gives a pretty good starting point for seeing whether their measures work. If the Brady center is right, then states that adopt more of their measures should see violent crime reduced. Note that I'm not graphing gun crime, because I honestly don't care whether I get killed with a knife or a gun. Done either way. I'm interested in the overall effect of Brady legislation on violence. The sources are included in the graphs, which came out a little bit big.
The result: effectively zero correlation. The R2 value shows how strongly they correlate. 1.0 is perfect, 0 is no relationship. The correlation between brady scores and crime rate is .000093, but in the wrong direction: states that have higher brady scores have very very slightly higher crime rates.
Now, what if there was some other thing that might reduce violent crime?
I also graphed % of population with concealed handgun licenses against violent crime. There turned out to be a slight correlation, just under 0.1. It's weak, but arguably present. Both graphs are below. My apologies again for the over-sized images.