SUGGESTIONS FOR FUTURE RESEARCH What is most remarkable about the CDC's review of studies of defensive gun use is how little was reviewed. A considerable body of literature has accumulated in the scientific and medical press about the incidence of defensive gun use, but very little of it was reviewed in the CDC report. The CDC report mainly confined itself to presenting the current controversy largely surrounding research studies on the incidence of DGU.

“Estimates of gun use for self defense vary widely, in part due to definitional differences in self-defensive gun use, different data sources and questions about accuracy of data, particularly when self-reported. The NCVS [National Crime Victim Survey] has estimated 60,000 to 120,000 defensive uses of guns per year (McDowell et al. 1998). Another body of research estimated annual gun use for self defense to be much higher, up to 2.5 million incidents, suggesting that self defense can be an important crime deterrent (Kleck and Gertz, 1995).” (CDC report, pg. 45-46) “Defensive uses of guns by crime victims is a common occurrence, although the exact number remains disputed (Cook and Ludwig, 1996, Kleck 2001a). Almost all national survey estimates indicate that defensive gun use by victims is at least as common as offensive uses by criminals, with estimates of annual uses ranging from about 500,000 to more than 3 million per year (Kleck, 2001a), in the context of about 300,000 violent crimes involving firearms in 2008 (Bureau of Justice Statistics, 2010). On the other hand, some scholars point to radically lower estimates of only 108,000 annual defense if use is based on the national crime victimization survey (Cook et al., 1997). The variation in these numbers remains a controversy in the field. The estimate of 3 million defensive uses per year is based on an extrapolation from a small number of responses taken from more than 19 national surveys. The former estimate of 108,000 is difficult to interpret because respondents were not asked specifically about defensive gun use. (CDC report, pg 15) (emphasis added). Sadly, the CDC reports says little more than that researchers disagree on the true incidence of DGU in America. Sadder still, the CDC report makes no suggestions for further studies to better understand the incidence of DGU or resolve the disagreement among investigators. In my opinion, knowing accurately how frequently gun owners use their guns to stop or prevent criminal attack is a necessary step in formulating sound and effective gun policy in this country. Research to accurately assess the incidence of DGU should continue and receive the full attention of the medical and public health community. One problem in accurately assess the incidence of DGU is determining what is and what is not a DGU. The CDC report acknowledges that “definitional differences” play a role in the wide variations in DGU estimates found by different research teams. Investigators who seek to measure DGU must first agree on a definition of DGU. The CDC and the National Research Council (NRC) can help end the ambiguity about what is and what is not a DGU by formulating a solid and acceptable definition of DGU. The CDC and their committee of senior investigators is remiss in not taking the opportunity of the publication of their presidentially-mandated review to put forth some suggestions for an research-oriented definition of DGU. Unlike gunshot injuries, which are directly counted by police and hospitals, the incidence of defensive gun use must be estimated. We know with a high degree of certainty how many people get shot by guns every year. Anyone killed by a bullet is going to be examined by the police and a state coroner. The vast majority of people with a gunshot injury will receive some sort of treatment by a physician or hospital. Police, coroners, doctors and hospital all keep very thorough records of deaths and injuries. So counting the number of gunshot injuries and deaths involves little more than collecting records from police departments and hospitals. The yearly counts of people injured and killed by gunshot are backed and verifiable by examining those police and hospital records. This gives the counting of gunshot injuries an almost unassailable credibility: even the gun industry acknowledges the accuracy of statistics on gunshot injuries. In contrast, DGUs cannot be directly counted, but have to be estimated. Police and hospitals do not keep track of DGUs, nor investigate DGUs as crimes are investigated, so currently there is no way to directly count DGUs. The most common way to estimate DGUs is to do a survey: the researchers pick a number of people who they think are representative of the area or region they are investigating, and then ask those people if they have used their guns defensively. The incidence of DGU is that area or region under study is then calculated from the responses of those surveyed. This method of estimation depends on a couple of critical methodological factors:

- the selection of the sample to be surveyed;

- the formulation of the survey questions;

- determining what is and what is not a DGU;

- the accuracy of the study subjects' responses;

- how the investigators deal with those who decide not to respond to the

survey;

- the mathematics the investigators use make their estimations from the

survey data. So if we are to have accurate annual counts of the incidence of DGU, as we do with gunshot injuries, it makes sense to instruct our national law enforcement agencies to start collecting records of DGU, and to investigate DGU with the same seriousness and scrutiny given to statistics of gunshot injuries and deaths. In summary, the CDC report said very little about DGU, and made no useful recommendations for the further study of DGU in America. Accurately knowing the incidence of DGU in America is important for formulating effective gun policy in America. More research is needed to accurate know the incidence of DGU, and our national law enforcement agencies should be asked to directly count DGU and report on the yearly occurrence of DGU, as gunshot injuries are counted and reported yearly. Investigators who wish to accurately count DGU must first agree on a useful definition of DGUs. Our next article in this series will focus on defining what is and what is not a defensive gun use. Defensive Gun Use - You Decide will be published by the Firearm Law and Policy group later this week. To see a list of all the original and republished Firearm Law and Policy diaries, go to the Firearms Law and Policy diary list.