I need to do a bit more research on his paper. Lott has already come out with a few criticisms of the paper. Duggan has three things going for him: he is a Harvard PhD, he is at the University of Chicago, and he go the paper published in a really good journal.
I think he is wrong because he has not properly accounted for neighborhood effects. He is looking at a 10-year lag of gun magazine readership (I think he only had subscription info for one or two gun mags). The problem is that gun magazine readership is also pretty correlated to certain demographic groups: young, ex-military, blue-collar, male. They are the sorts of folks who will live in a marginal neighborhood, and also those demographics decribe areas that have gone "black" over time. Think of areas like the southwest side of Chicago, Newark and other areas of close-in New Jersey, and PG County, Maryland just outside of DC. In the past those areas were mostly white and had low crime rates. The demographics changed fast and they suddenly have a lot of murders. PG County, Maryland, is all suburban. There is no inner-cityness about it, but so far this year they have had more murders than the entire Minneapolis-St. Paul metro area.
There are statistical ways to correct for these neighborhood effects. I wonder if Duggan would give me his data set to work on?
GunLvr