After a year or so, they did a study that showed that concealed-carry license-holders were less likely than the general population to be arrested on any charge, not just gun-related offenses. It became very clear that those of us who legally own and carry firearms are pretty law-abiding folks.
I don't think the CHL permit really has much to do with it - I think it's more a matter of "law-abiding folks are pretty law-abiding".
When you look at CHL holders, you're looking at a subset of the entire population; one who generally haven't been convicted of felonies or domestic violence crimes, and who have not been committed to a mental health facility for treatment. That right there is going to eliminate a big source of criminal activity - repeat offenders and those who have previously been diagnosed with mental disorders.
I'd be curious to know how the arrest rate for CHL holders compares to the arrest rate of people who are eligible to have a CHL, but don't.