GAO study on CCW permits
Here, in pdf. It finds:
8,000,000 ccw permits have been issued.
Virtually the entire country, apart from Ill, Calif, and some NE states, has gone with "shall issue," or does not require a permit for concealed carry.
Revocations are rare (p. 26). Arizona had issued 12,000 permits, and revoked 30 (I assume these are annual figures, since total permits are much higher). Texas had issued 143,000 and revoked 900.
Data is also broken down by State (p. 78 ff). Florida has about 887,000 active permits, while Hawaii has zero. Pennsylvania has 786,000; Maryland has 12,000. Someone with spare time could compute out the ratio of permits to population, and compare that to crime rates.
UPDATE: GAO was requested to study CCW laws by, I believe, Nancy Pelosi, in hopes that they'd find data that she could use to argue against nationwide CCW reciprocity, by finding that standards vary widely. Which is pretty much the case. However, since permit holders seem to be quite law abiding whatever the standards are, the results are likely disappointing to her.