I'm not sure that "more guns" in Lott's thesis means "higher ownership" -- but rather, "more guns in places where crimes occur" ... he says specifically that even with liberal CCW laws, very few people will take the time to get one (I think in Florida they are seeing 2-4% of the eligible population) and even fewer will take the time to carry. It's a pain: you have to carry around a big piece of steel on your hip. You have to make sure that no one sees you carrying it (it's usually grounds for losing your permit if a Concerned Citizen sees you carrying and calls the cops, worried that you're a Bad Guy), which means that on a hot day you're the one wearing a windbreaker. Women (like Dianne Feinstein, Gun Control Champion that she is) can of course keep them in a pocketbook or something.
Everyone I know who carries complains about it, which I guess is about as good as you could hope for.
Lott tries pretty hard, but I think an easier "sell" would be to show that it wouldn't be as bad as you think to let people carry if they wanted to, and it might just have some benefit.
But as for Duggan, I don't get it. Gun ownership is up (despite the data set that he uses to show that the number of _households_ with guns is down; aren't fewer people truthfully saying "yes" to the question?) and the murder rate is at historic lows. I read yesterday that Oakland's murder rate is half what it was at the start of the 90's.
There's something going on, but it's not correlated to ownership.