In the post about Gun Facts from a couple days ago Reader Kelly asks:
Good question. I did a quick scan of the report but couldn't find how they parsed their data. It's probably in there but it's 125 pages and I don't have time to read through it all right now. I'll do that over the course of the week (fun 4th of July activity!) and get back to you.
The report is easy enough to follow that I recommend anyone with a passing interest give it a read or at least a quick scan. The subject is near and dear to my (cold/dead/empty) heart so I'll give it a thorough review.
You can download your own copy if you give the National Academy of Sciences your email address or view a shared version on google drive.