5/29/03

An interview about my new book, The Bias Against Guns, can be found at The Illinois Leader. A discussion of a presentation that I recently made here at the American Enterprise Institute can be found at The Bias Against Guns, May 20, 2003.

Today the "big" controversy seems to involve a sentence in a footnote from a paper that John Whitley and I wrote on safe storage gun laws (so-called child protection acts) in the October 2001 Journal of Law and Economics. It is certainly flattering that people read the papers so carefully. The charge, addressed in an e-mail to me and sent to firearms discussion groups, is that footnote 32 on page 668 incorrectly discusses a paper by Peter Cummings, David Grossman, Frederick Rivara, and Thomas Koepsell that was published in the October 1997 Journal of the American Medical Association. Our footnote says that:

"While the Cummings et al. piece examined national data, they did not use fixed year effects which would have allowed them to test whether the safe storage states were experiencing a drop relative to the rest of the country."

We had been unable to replicate their claimed results using fixed effects and the only way we could get something similar was without fixed effects. It really shouldn't have been that difficult for us to confirm what they found since we were used their dates for the laws. Unfortunately, Cummings, Grossman, Rivara, and Koepsell were unwilling to give us their data when we asked for it. I asked for the data from Cummings and one other coauthor. I also told them what I had found regarding the fixed effects and Cummings didn’t disagree with me. Possibly we should have made a big deal of yet more academics who refused to share their data, but we decided that the more straightforward approach would be to simply say what we found. Alternatively, we could have simply stated that we were unable to confirm their results. For those interested, our data is readily available by following the links at the bottom of the page for www.johnlott.org.

Update:

Another aspect of this discussion which people apparently do not understand is the difference between examining changes in before-and-after trends in a state's accidental death rates and differences in before-and-after averages. Take a simple case where accidental gun deaths were falling before the law and continued to fall at exactly the same rate afterwards. In that case, a simple before-and-after average would indicate that the law had reduced accidental gun deaths, but it would be pretty obvious from looking at the data that a pre-existing trend had simply continued at exactly the same rate and that the law had no impact. Unlike the work that Whitley and I have done, the Cummings, Grossman, Rivara, and Koepsell piece merely examines the simply before-and-after averages.