The other day, I published this scatter-graph of 48 U.S. states to show there is no significant correlation between gun homicides and gun ownership by state. The plot relies on the recently released FBI data for 2014 (the FBI lacks data for Alabama and Florida). The state gun ownership rates come from a study published this summer by Injury Prevention.
Whether or not you include D.C. (the chart above does not, but if you do the trend line goes just slightly negative), there was no significant correlation in 2014.
I figured that perhaps I'd find a different story if I plotted out another crime that is most often committed with guns — robbery. I was wrong. There's no significant correlation there either.
Note that although the slope of the trend line is negative this time, the correlation is too weak to be considered significant. It overstates the case to say that more guns mean fewer gun robberies.
And here's a more detailed look at gun and non-gun robbery rates in 48 states (the FBI has data for Florida and Alabama this time, but not Illinois and Hawaii) ranked from right to left by the incidence of robberies committed with firearms.
The point here is that at least in 2014, there wan't any correlation between a given state's rate of gun ownership and its rate of these two gun crimes. Given that most people think of gun control as a crime-reduction measure, this seems to be at least a fact deserving of mention.