Or is the possibility that you may be armed supposed to act as a deterrent?
The bad thing about CCW is it turns any assault into a likely-to-end-in-someone-shot situation; if you're carrying and potentially will be knocked unconscious in an assault, or are being grappled, the attacker may grab your gun and shoot you; your correct course of action is to shoot him first.
[1] http://en.wikipedia.org/wiki/United_States_cities_by_crime_r...
Violent crime tends to be closely related to poverty, and much tends to be "criminal-on-criminal". As criminals do not follow carry laws, it's hard to know the true effect on stats. I do find it interesting that if you sort the list by property crime, the top cities are dominated by ones in gun friendly states. A quick comparison shows for example, Atlanta has a higher property crime to violent crime ratio than Oakland. If you say there's "base crime level" driven by socioeconomic factors, then Atlanta's more gun friendly laws could contribute to it having a smaller percentage of violent crime in the total crime pie chart. Criminals may choose to break into unoccupied cars, stores, and homes instead of muggings and home invasions.