Lott responds to my critique of his AEI talk

Lott has responded to parts of my post yesterday.

1) "Why do you use the government's survey estimate for the number of crimes committed with guns but use other surveys in your two books for estimates on the number of defensive gun uses?"

The problem with the survey from the Bureau of Justice Statistics is that "virtually none of the victims who use guns defensively tell interviewers about it in the [National Crime Victimization Survey]" (Kleck, Targeting Guns, p. 2250. People aren't allowed to say whether they have used a gun defensively unless they indicate that they have had a crime committed against them. As many people who used a gun defensively may have prevented a crime, and thus have avoided an incident serious enough to be included in the set of events asked by the interviewer, many successful defensive gun uses would never be recorded.

The NCVS asks questions like "Did anyone TRY to rob you?" Certainly it would not count a case where the defender used a gun to scare off a suspicious looking character before he made a move, but that isn't a defensive use, it's assault with a deadly weapon.

2) "Is it accurate to describe the students who stopped the attack as having law enforcement backgrounds?"

The students were attending law school in Virginia and were on leave from their deputy sheriff jobs in another state, North Carolina.

As Lott is well aware from the discussion he was involved in, Bridges and Gross were police officers. Lott's description of them as merely having a law enforcement background implies that they were former police officers.

3) Does the New York Times actually claim that the "rampage" killings were increasing during the 1990s?

The first article (April 9, 2000) in the series contains a massive table that shows very clearly that most of the attacks over the last 50 years supposedly occurred within the last five years.

"The series of articles published in The Times this week based on that research offered several new insights. Although such killings account for only one-tenth of 1 percent of all homicides, the series confirmed the public perception that they appear to be increasing." Editorial, "A Closer Look at Rampage Killings," New York Times, April 13, 2000, p. A30.

In fact, the Times says

the database does not include every attack of this type over the last 50 years.

The reference from the editorial is to this passage, about a different dataset:

Yet there is a strong impression that they have become more common. In an effort to confirm the trend, The Times analyzed F.B.I. reports of all homicides since 1976. Each year there were 15,000 to 22,000 homicides, but very few involved three or more victims.

That universe shrank even more, to just a few dozen, when The Times weeded out those involving robbery or gang violence, and those in which the primary victim was a family member.

What is left is the closest thing there is to a census of rampage killings --- about one-tenth of one percent of all killings.

And it shows that in the 1990's, they increased.

Their number remained fairly consistent from 1976 to 1989, averaging about 23 a year, only once going above 30. But between 1990 and 1997, the last year for which data was available, the number averaged over 34, dipping below 30 only once, in 1994.

So, yes, they do say that such killings increased, from 23 a year to 34 a year. They don't say that they increased nine-fold as Lott claimed. And they base their claim on FBI data of all such killings, not on a database of just 100 cases.

4) "Why did you use the CBS and Voter News Service surveys for gun ownership in your book More Guns, Less Crime but use the General Social Survey in your book The Bias Against Guns?"

The CBS and Voter News Service surveys have the advantage in that they are very large surveys (e.g., the VNS survey interviewed over 30,000 people). That makes it possible to get a fairly accurate measure of gun ownership rates in individual states. The problem with these surveys is that they cover only two years, 1988 and 1996. By contrast, the GSS has a very small sample in any given year, but the survey covers most states every other year. Which survey you use depends upon the questions that you want to ask. In the current book, The Bias Against Guns, states have adopted safe storage gun laws over many different years from 1989 to 1998 during the period that I studied. The question that I wanted to apply the survey data to was how gun ownership rates changed in the different states that adopted these laws in different years (see pp. 177 to 179 in the book). For the general question addressed in More Guns, Less Crime on whether the places with the biggest relative increases in gun ownership had the biggest relative drops in violent crime (pp. 113-14), I wanted to use the largest surveys available to get as accurate a measure as possible of the differences in gun ownership rates across states. However, in the chapter on gun storage laws in The Bias Against Guns, it was desirable to see how gun ownership rates changed immediately before and after the adoption of the law and the only way that I could do that was with the GSS data.

The GSS sample size is much too small to give a meaningful estimate of gun ownership rates in a given state. About the only way it could be used for this would be to pool many years of data, but then you get no indication of "how gun ownership rates changed immediately before and after the adoption of the law".

Lott's discussion of the CBS and VNS surveys is also misleading. While the CBS survey had a very large sample, the VNS survey, with a sample of 3,818 isn't much larger than the GSS, and when you are considering the accuracy of differences between the two surveys it is the sample size of the smaller one that matters most.

Neither of Lott's reasons seems like a good one, and he he still hasn't addressed the fact that the surveys give opposite results---the GSS shows gun ownership declining, while the CBS+VNS polls show gun ownership increasing.

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