What Do CDC’s Surveys Say About the Prevalence of Defensive Gun Use?

Abstract

In 1996, 1997, and 1998, the Centers for Disease Control and Prevention (CDC) conducted large-scale surveys asking about defensive gun use (DGU) in four to seven states. Analysis of the raw data allows the estimation of the prevalence of DGU for those areas. Data pertaining to the same sets of states from the 1993 National Self-Defense Survey (Kleck & Gertz, 1995) allow these results to be extrapolated to the U.S. as a whole. Possible sources of error in surveys of DGU are reviewed, and the results of previous surveys compared. CDC’s survey data confirm previous high estimates of DGU prevalence, disconfirm very low estimates derived from the National Crime Victimization Survey, and indicate that defensive uses of guns by crime victims are far more common than offensive uses by criminal offenders.

Appendix

The following adjustments were applied to the Table 4 DGU prevalence percentages in order to make them more comparable with each other.

• Adjustment 1 was applied to surveys inquiring about a five-year recall period, in order to produce an estimate pertaining to a one-year recall period. The NSDS obtained a DGU prevalence of 1.326 when using a one-year recall period, and 3.315 when using a five-year recall period (Kleck & Gertz, 1995, p. 184). Therefore, adjustment 3 consisted of multiplying a prevalence figure based on a five-year recall period by 0.40000 (1.326/3.315 = 0.40).

• Adjustment 2 was applied to surveys using a lifetime recall period (“have you ever. .. “), in order to produce an estimate pertaining to a one-year recall period. A California poll was unique in asking a DGU question for both a one-year recall period and a lifetime recall period, and indicated that the same survey yielded a 1.4 percent prevalence figure for a one-year recall period and an 8.6 percent figure for lifetime period (Field Institute, 1976), so the adjustment consists of multiplying an “ever used” estimate by 0.16279 (1.4%/8.6%=0.16279).

• Adjustment 3 was applied to surveys that failed to exclude uses of guns against animals, in order to produce an estimate pertaining only to uses against humans. The NSDS (Kleck & Gertz, 1995) indicated that of 244 Rs initially reporting DGUs, 22 had used guns only against animals, so the adjustment consists of multiplying a humans-plus-animals estimate by 0.90984 (222/244).

• Adjustment 4 was applied to surveys that failed to exclude incidents linked with military, police, or security guard duty. An experiment by McDowall et al. (2000) showed that when Rs were not instructed to exclude such incidents, 30 of the 155 Rs who initially reported a DGU were found to be reporting these kinds of duty-related experiences. The adjustment consisted of multiplying the DGU prevalence percentage by 0.806 (125/155 = 0.806).

• Adjustment 5 was applied to surveys that asked only about DGUs committed with handguns. Kleck and Gertz (1995, p. 185) found that 79.7% of DGUs were committed with handguns, so the adjustment consisted of multiplying a handgun-only DG prevalence percentage by 1.255 (100/79.7 = 1.255).

• Adjustment 6 was applied to a survey that inquired only about DGUs occurring outside the R’s home. Kleck and Gertz (1995) that only 62.7% of DGUs occurred outside the user’s home, so the adjustment consisted of multiplying the DGU prevalence percentage by 1.595 (100/62.7 = 1.595).

• Adjustment 7 was applied to a survey that asked only about burglary-linked DGUs. Kleck and Gertz (1995) found that 33.8% of DGUs were linked with burglaries, so the adjustment consisted of multiplying the DGU prevalence percentage by 2.959 (100/33.8 = 2.959).

• Adjustment 8 was applied to surveys that asked the DGU question only of Rs who reported personally owning a gun or handgun, in order to produce an estimate pertaining to the entire population and thus reflecting uses among those who do not report current ownership of a gun. The NSDS indicated that only 59.5% of Rs reporting DGUs reported current personal ownership of a gun (Kleck & Gertz, 1995, p. 187), so the adjustment consists of multiplying a gun-owners-only estimate by 1.681 (1/0.595 = 1.681).

• Adjustment 9 was applied to surveys that asked the DGU question only of Rs who lived in households reporting current gun ownership, in order to produce an estimate pertaining the entire population and thus reflecting uses among those who do not live in a household reporting current ownership of a gun. The NSDS indicated that only 79.0% of Rs reporting DGUs reported current household ownership of a gun (Kleck & Gertz, 1995, p. 187), so the adjustment consists of multiplying a gun-owning household-only estimate by 1.26582 (1/0.790).

• Adjustment 10 was applied to the 1989 Time/CNN survey that only asked about DGUs in which the gun was fired. Kleck and Gertz (1995, p. 185) found that only 23.9% of DGUs involve the gun being fired, even as a warning shot, so the adjustment consisted of multiplying the guns-fired DGU prevalence by 4.184 (100/23.9 = 4.184).

• Adjustment 11 was applied to the 1978 Cambridge Reports survey, which only asked the DGU question of Rs who reported personally owning a handgun for purposes of “protection.” Analysis of the NSPOF dataset shows that only 27.69% of DGUs were by Rs who personally owned a handgun primarily for self-protection, so the adjustment consisted of multiplying the unadjusted DGU prevalence by 3.6111 (100/27.69 = 3.6111).

• Adjustment 12 was applied to the 1991 Gallup poll, which only asked the DGU question of Rs who reported household handgun ownership at the time of the survey. Analysis of the NSPOF dataset shows that only 40.46% of DGUs were by Rs who lived in a household with handguns, so the adjustment consisted by multiplying the unadjusted DGU prevalence by 2.4717 (100/40.46 = 2.4717).