What Data Is Needed to Study Concealed Carry?
As Ciara McCarthy notes over at Slate, all 50 states now have laws that allow residents to carry concealed weapons, and only one state (Nevada) allows unfettered access to the identities of the permit holders. McCarthy argues that this stops researchers from properly analyzing the effects of concealed-carry laws. Without knowing who permit holders are, it's hard to tell whether permit holders are committing crimes.
On the other hand, gun-rights supporters offer reasons as to why permit data shouldn't be public; for example, a list of permit holders would be useful to criminals looking to steal guns (or looking to steal other things without getting shot). But fortunately, there are several ways we can study the behavior of concealed-carry permit holders without making their identities public.
For example, we can look at permits that are revoked because people committed crimes. The pro-gun scholar John Lott has argued, based on state data as well as collected news reports that mention when criminals have carry licenses, that permit holders commit crimes at rates much lower than the general population. (See also the third edition of Lott's More Guns, Less Crime.) However, this method relies on an assumption that states' systems for revoking permits are reliable (and otherwise bad behavior by permit holders will show up in news reports), which might not be true. Lott himself has noted that many states don't keep detailed records about how many permits are revoked and why.*
States could also reveal the concealed-carry status of all individuals convicted of gun-related crimes. This would leave law-abiding permit holders anonymous while giving researchers a better way to tell how many permit holders are not law-abiding. And a law to this effect would be much easier to pass than a law making permit data completely public.
Even a survey asking permit holders whether they have used their guns defensively doesn't require public records. Any researcher is free to call people and ask whether they have permits to put together a sample, though this method may not not be particularly accurate or efficient (in Florida, for example, only about 5 percent of residents have permits). Alternatively, a state could commission a survey itself, giving a select few researchers access to the list on the condition that the information remain confidential.
It's also worth bearing in mind that, according to some theories about the effects of concealed carry, the policy works through deterrence -- that is, because the weapons are concealed, it makes criminals think twice about victimizing innocent and seemingly vulnerable people. Obviously, no data about the behavior of permit holders can shed light on this phenomenon.
And lets not forget that, despite the overall trend of states' refusing to release identification data, newspapers in numerous states have used public-records requests to publish lists of permit holders' names.
This is a complicated issue, and years of intense statistical research have not produced many strong results. But there are ways to improve data collection -- even starting with the political reality that full disclosure of permit holders' names is unlikely.
* This paragraph has been amended to reflect that fact that state revocation numbers are not only data source.