Earlier I observed that Lott had claimed that a paper by Cummings et al that found a significant decline in juvenile accidental gun deaths following the introduction of safe storage laws was
widely discredited because the researchers never factored in that accidental gun deaths have been falling everywhere for decades.
When I pointed out that their paper clearly stated that they had controlled for national trends by using fixed effects, Lott responded with:
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. 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.
Firstly, I note that Eugene Volokh had no difficulty obtaining Cummings’ raw data. More importantly, in an article Reexamining the association between child access prevention gun laws and unintentional shooting deaths of children by Webster and Starnes I find that:
- Webster and Starnes gathered their own data:
“Data on the annual number of unintentional gunshot deaths among children 0 to 14 years old and on population demographics were obtained for each state and the District of Columbia from the Compressed Mortality Files of the National Center for Health Statistics for the years 1979 through 1997
- Webster and Starnes included fixed year effects:
“Year dummy variables were also used to control for temporal variation observed across states, irrespective of their CAP law status, attributable to unmeasured factors (eg, prevalence of gun ownership).
- Webster and Starnes replicated Cummings’ results:
“Using the same data and methods used by Cummings et al, we first replicated their findings.
Lott’s original claim that Cummings did not use fixed year effects is false. His new claim that Cummings’ results could not be replicated is also false.
The most likely explanation of all this is that in his book Lott made a mistake about Cummings. Perhaps he carelessly confused their paper with some other paper that didn’t use fixed effects. When I pointed out his error, rather than admit to making a mistake, Lott made up the story about only being able to replicate Cummings without fixed effects.