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Defensive gun use (DGU) is the use of a firearm in self-defense or defense of others. The frequency of defensive firearms incidents, and their effectiveness in providing safety and reducing crime is a controversial issue in gun politics and criminology.〔Harry L. Wilson, ''Guns, Gun Control, And Elections: The Politics And Policy of Firearms'', ISBN 0742553485, Rowman & Littlefield, 2007.〕 Different authors and studies employ different criteria for what constitutes a defensive gun use which leads to controversy in comparing statistical results. Perceptions of the number of DGUs dominate discussions over gun rights, gun control, and concealed carry laws. ==Estimates of frequency== Estimates over the number of defensive gun uses vary wildly. Ranging between a high end of 33 Million incidents per year and a low end of 127 incidents per year, depending on the study's definition of a defensive gun use, survey design, population, criteria, time-period studied, and other factors. The higher end survey estimating between 12.9 and 33.1 Million annual defensive gun uses comes from a 1994 telephone survey titled The National Survey of Private Ownership of Firearms performed by the firm Chilton Research Services . A commonly cited estimate by Kleck and Gertz shows between 1 to 2.5 million DGUs in the United States each year.〔〔J.N. Schulman, Guns, Crimes and Self-defense, Orange County Reg., Sept. 19, 1993, at 3.〕〔Gary Kleck & Marc Gertz, "Armed Resistance to Crime: The Prevalence and Nature of Self-Defense with a Gun," 86 ''J. Crim. L. & Criminology'' 150 (1995).〕 Another estimate has estimated approximately 1 million DGU incidents in the United States.〔〔 Lower end estimates include that by David Hemenway, a professor of Health Policy at the Harvard School of Public Health, show approximately 55,000-80,000 such uses each year.〔(David Hemenway, ''Chance'', Vol 10, No. 3, 1997. )〕〔(Journal of Criminal Law and Criminology (Northwestern) 87 (1997): 1430. )〕 At the low end, a recent study of data from the National Crime Victimization Survey (NCVS) identified only 127 self defensive gun uses per year. The National Self-Defense Survey and the National Crime Victimization Survey (NCVS), vary in their methods, time-frames covered, and questions asked.〔Committee on Law and Justice, ''Firearms and Violence: A Critical Review'' (2004) ISBN 0-309-09124-1, page 103.〕 DGU questions were asked of all the NSDS sample.〔 Due to screening questions in the NCVS survey, only a minority of the NCVS sample were asked a DGU question.〔(Philip J. Cook and Jens Ludwig, "Guns in America: National Survey on Private Ownership and Use of Firearms" ), NIJ Research in Brief, May 1997.〕 Estimates of DGU from the NCVS are consistently lower than those from other studies. A 2000 study suggested that this may be because the NCVS measures different activities than the other surveys do. Besides the NSDS and NCVS surveys, ten national and three state surveys summarized by Kleck and Gertz gave 764 thousand to 3.6 million DGU per year.〔 Hemenway contends the Kleck and Gertz study is unreliable and no conclusions can be drawn from it.〔 He argues that there are too many "false positives" in the surveys, and finds the NCVS figures more reliable, yielding estimates of around 100,000 defensive gun uses per year. Applying different adjustments, other social scientists suggest that between 250,000 and 370,000 incidences per year. Another survey including DGU questions was the National Survey on Private Ownership and Use of Firearms, NSPOF, conducted in 1994 by the Chiltons polling firm for the Police Foundation on a research grant from the National Institute of Justice. NSPOF projected 4.7 million DGU per year by 1.5 million individuals after weighting to eliminate false positives.〔 Discussion over the number and nature of DGU and the implications to gun control policy came to a head in the late 1990s.〔〔(Otis Dudley Duncan, "Gun Use Surveys: In Numbers We Trust?" ), ''Criminologist'', v25 n1, Jan/Feb 2000.〕 A study published in 2013 by the Violence Policy Center, using five years of nationwide statistics (2007-2011) compiled by the federal Bureau of Justice has found that defensive gun uses (DGU) occur at a dramatically lower magnitude than that suggested by Kleck: an average of 67,740 times per year.〔http://www.vpc.org/studies/justifiable.pdf, retrieved 10/29/2014〕 In the report "Guns in America: National Survey on Private Ownership and Use of Firearms" by Philip J. Cook and Jens Ludwig, the authors quote the National Crime Victim Survey (NCVS) as finding 108,000 DGU per year. The gun use survey included in the NSPOF itself projected 4.7 million DGU which Cook and Ludwig explained by pointing out all of the NSPOF sample were asked the DGU question. Cook and Ludwig also compared the U.S. crime rate to the number of DGU reported by Kleck and similar studies and said that their estimate of DGU is improbably high. A 1994 study examined NCVS data and concluded that between 1987 and 1990, there were approximately 258,460 incidents in which firearms were used defensively in the United States. The same study said that "Firearm self-defense is rare compared with gun crimes." An article published by the Bureau of Justice Statistics, drawing its DGU from the NCVS, said: "In 1992 offenders armed with handguns committed a record 931,000 violent crimes ... On average in 1987-92 about 83,000 crime victims per year used a firearm to defend themselves or their property. Three-fourths of the victims who used a firearm for defense did so during a violent crime; a fourth, during a theft, household burglary, or motor vehicle theft." Cook and Ludwig said of the NCVS, NSPOF, and Kleck surveys: "The key explanation for the difference between the 108,000 NCVS estimate for the annual number of defensive gun uses and the several million from the surveys discussed earlier is that NCVS avoids the false-positive problem by limiting defensive gun use questions to persons who first reported that they were crime victims. Most NCVS respondents never have a chance to answer the defensive gun use question, falsely or otherwise."〔 Clayton Cramer and David Barnett say that such a structure could cause the NCVS to under-count defensive gun uses, because someone who has successfully defended themselves with a gun may not consider themselves a "victim of a crime." In the NCVS, if one says that they have not been a victim of a crime, the survey assumes that there was no attempted crime and does not go on to ask if they have used a gun in self-defense.〔(Clayton Cramer and David Barnett, "Tough Targets: When Criminals Face Resistance From Citizens" ) CATO Institute, 2012, p.8〕 Kleck gives another explanation of the discrepancy, which is that the NCVS estimate is too low because it never asks a respondent about defensive gun use. (He says that it asked a generic, open-ended question about anything that the victim might have done for self-protection.)〔 Kleck says that many other surveys (at least 20) have likewise obtained huge estimates of DGU frequency, from 500,000 to over 3 million per year -common enough to outnumber criminal uses〔Kleck, G. and D. Kates (2001), Armed: New Perspectives on Gun Control, Chapter 6. N.Y.: Prometheus〕 and further notes that studies of methodological errors in surveys concerning other crime-related behaviors and experiences have consistently found that the errors produce, on net, ''under''estimates of the frequency of the behaviors, including victimization experiences, offending behavior, and gun ownership.〔 He has said that critics' assessment of possible errors in surveys are one-sided - that they consider only flaws that would contribute to overestimation of defensive gun use frequency. Kleck says that critics fail to take into account of flaws that would contribute to an underestimation of defensive gun uses, such as a tendency of survey respondents to conceal or otherwise fail to report controversial acts they have committed, victimization experiences, and gun ownership. He says that it is logically impossible to determine whether surveys overestimate or underestimate the prevalence of such experiences if one does not establish the relative balance of the two kinds of error.〔 Kleck asserts errors in his critics' statements that his survey's estimates of defensive gun uses linked with specific crime types, or that involved a wounding of the offender, are implausibly large compared to estimates of the total numbers of such crimes. The total number of nonfatal gunshot woundings, whether medically treated or not, is unknown, and no meaningful estimates can be derived from his survey regarding defensive gun uses linked with specific crime types, or that involved wounding the offender, because the sample sizes are too small. The fact that some crime-specific estimates derived from the Kleck survey are implausibly large is at least partly a reflection of the small samples on which they are based - no more than 196 cases. Kleck states that his estimate of total defensive gun uses was based on nearly 5,000 cases. Thus, he argues, the implausible character of some estimates of small ''subsets'' of defensive gun uses is not a valid criticism of whether estimates of the ''total'' number of defensive gun uses are implausible or too high.〔 Criminologist Marvin Wolfgang, who described himself "as strong a gun-control advocate as can be found among the criminologists in this country" and whose opinion of guns was "I would eliminate all guns from the civilian population and maybe even from the police. I hate guns--ugly, nasty instruments designed to kill people" defended Kleck's methodology, saying "What troubles me is the article by Gary Kleck and Marc Gertz. The reason I am troubled is that they have provided an almost clear-cut case of methodologically sound research in support of something I have theoretically opposed for years, namely, the use of a gun in defense against a criminal perpetrator". He went on to say that the NCVS survey did not contradict the Kleck study and that "I do not like their conclusions that having a gun can be useful, but I cannot fault their methodology. They have tried earnestly to meet all objections in advance and have done exceedingly well." 〔(Marvin E. Wolfgang, "A Tribute to a Position I Have Opposed" ), ''Journal of Criminal Law and Criminology'', Vol 86 No 1, Fall 1995, page 188.〕〔Marvin E. Wolfgang, "Remarks of Marvin E. Wolfgang at the Guns and Violence Symposium", ''Journal of Criminal Law and Criminology'', Vol 86 No 2, Winter 1996, page 617.〕 However, both Kleck and Gertz' and Lott's research have come under considerable fire from the academic community. Critics such as Hemenway have pointed to the fact that their study ignores problems that arise from telescoping, the social desirability bias, and strategic responses by gun rights advocates, all of which can lead to significant false positives.〔(【引用サイトリンク】title=The Myth Behind Defensive Gun Ownership )〕 In addition, a 2004 study surveyed the records of a Phoenix, Arizona newspaper, as well as police and court records, and found a total of 3 instances of defensive gun use over a 3.5 month period. In contrast, Kleck and Gertz's study would predict that the police should have noticed more than 98 DGU killings or woundings and 236 DGU firings at adversaries during this time. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Defensive gun use」の詳細全文を読む スポンサード リンク
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