Peter Boucher writes:

Just in case anyone's interested.

Copied from Kleck/Gertz, here are the polls from table 1

(minus those with no estimate of annual DGUs):Survey, Where, What year, What kinds of guns, # DGUs

Field, California, 1976, just handguns, 3.1M

Bordua, Illinois, 1977, all guns, 1.4M

DMIa, U.S., 1978, all guns, 2.1M

DMIb, U.S., 1978, all guns, 1.1M

Hart, U.S., 1981, just handguns, 1.8M

Ohio, Ohio, 1982, just handguns, 0.8M

Mauser, U.S., 1990, all guns, 1.5M

Gallup, U.S., 1991, all guns, 0.8M

Gallup, U.S., 1993, all guns, 1.6M

L.A.Times, U.S., 1994, all guns, 3.6M

Tarrance, U.S., 1994, all guns, 0.8M

I've just spent a couple of hours figuring out how Kleck computed

these estimates. Kleck acknowledges that all these polls have

deficiencies when used to attempt to estimate DGUs, so he applies

various correction factors for these deficiencies to construct these

estimates. For example, the Ohio poll used a recall period of "ever",

only asked about handguns, and only asked respondents in handgun

households. So Kleck took the 6.5% who said they had used a gun,

multiplied it by the adult population of the US (190M), then

multiplied by 0.215 to correct for the question only being asked of

handgun households (I guess that he is estimationg that 21.5% of US

households have handguns), then multipled by 1.21 to correct for only

handgun uses being counted (1.21 is the ratio between all gun crimes

and gun crimes - Kleck seems to be assuming that the ratio will be

similar for DGUs) and finally multiplied by 0.237 to adjust the number

from "ever used" to "used in past year" (I don't know where this

number comes from - it seems way too high) to get an estimate of 0.8M.

These correction factors are rather arbitrary and different choices can

give wildly different results. For example, in "Point Blank", because

excluding defences against animals caused the percentage who used a

gun to drop from 12% to 7% in the DMIb poll, Kleck used a correction

factor of 7/12 to correct polls that did not exclude uses against

animals. In the Kleck/Gertz paper, this factor is not corrected for.

Another example: Since the average gun owner has had their guns for an

average of 20 years, a reasonable way to convert from a poll that

asked if the respondent had "ever used" to get uses per year, would be

to apply a correction factor of 1/20, rather than Kleck's 0.237. Just

make a different choice on these two factors causes the estimates

derived from some polls to come out in agreement with the NCVS, rather

than Kleck. For example, the estimate you get from the Bordua poll is

about 150k -- much closer to the NCVS than Kleck.

So, it cannot be said that all these polls support Kleck rather tan

the NCVS.

There is another very interesting thing about the numbers in Table 1

--- we can use them to test my hypothesis that a large number of the

gun uses are fabrications.

Some polls asked about handgun uses while others asked about all gun

uses. Now, since it is just as easy to make up a handgun use as any

sort of gun use, I would expect the percentage who used to be about the

same, no matter whether the question was asked about handguns or any

sort of gun. On the other hand, Kleck would expect the all guns polls

to give higher usage percentages by a factor of roughly 1.21. (Recall

that's the correction factor he uses for handgun-only polls).

So, I looked through table 1 and compared all the pairs of polls that

differed only in the handgun/any gun-use question. (That is, polls

that used the same recall period and so on.) For each pair I

calculated the ratio (all-gun poll)/(handgun poll). I expect this

ratio to be about 1, Kleck expects it to be 1.21.

The results:

Poll pair Ratio Field-Bordua 5/8.6 = 0.6 Hart-Mauser 3.79/4 = 0.9 Hart-Tarrance 2/4 = 0.5 Hart-Kleck 3.898/4= 1.0 Ohio-Gallup91 8/6.5 = 1.2 Field-LA Times 8/8.6 = 0.9 Mean ratio = 0.9

Of the six pairs, five come out closer to my 1.0 and one closer to

Kleck's 1.21.

Hence we can see that the polls in Kleck's table 1 show evidence that

the respondents have fabricated many of the DGUs reported.