DGU 25 Year Wars : Still Raging Strong

According to Pew Research (June 22, 2017), 67% of firearm owners cite protection as a major reason to own guns, a strikingly large number!

Dare break into ma house?

As to what exactly most firearm owners want to protect against, the research didn’t say. But I assumed, (forgive me if I’m wrong), that the majority of people want to protect themselves against ill-intent criminals, terrorist extremists and corrupt governments.

When we have higher firepower, we should be able to protect ourselves better, right?

However gun opposing groups say that guns are, in fact rarely used for protection. Instead they endanger their owners and people around them.

So who’s right and who’s wrong? Are guns effective protection tools? Without cold hard facts, it’s difficult to crack this billion dollar question.

Fortunately for us, many researchers have done the hard work of, um… research, and discovered many ground shattering revelations on this subject. The only tiny unfortunate thing for us is that many of these revelations contradict themselves.

So much for “Scientific Method”.

Table of Contents

DGU Definition = Don’t Give Up?

DGU, or “Defensive Gun Use”, is a prime research subject for many pro and anti guns data mongers as it could be used to quantify (somewhat) the effectiveness of “guns for protection”.

Here’s a definition of DGU from Wikipedia : “Defensive gun use (DGU) is the use or presentation of a firearm for self-defense, defense of others or in some cases, protecting property”.


The Face Palming Issue of DGU

Although DGU’s definition is defined, the subjectivity nature of “Defensive” and countless different circumstances lead to world-apart validation of DGUs between different research papers.

Imagine being in the shoes of a DGU data scientist. How are you going to collect these data?

A DGU defender might thwart an attack, and never report it to the police. While the criminal, wanting to evade prosecution, will likely not tell a soul either if he/she was not harm in the process.

Many DGU researchers decided to collect data by conducting surveys.

Since there are tons of factors when conducting a survey (sample selection, wording of the questions, question sequence); you probably can deduce how skewed, biased and misleading results can be if done incorrectly.

Guess what? Because of this we have the supposed DGU data from both camps (lovers & haters), saying the exact opposite things!


Quick Summary of DGU research and Critics

Year Author Research
Prior to 1995 Various At least 14 research, including the NCVS;
Estimated annual DGU ranges from 80,000 to 3,609,682
1995 Gary Kleck & Marc Gertz Armed Resistance to Crime: The Prevalence and Nature of Self-Defense with a Gun; Also called NSDS (National Self-Defense Survey)
Estimated 2.2-2.5 million annual DGU cases
1995 Marvin Eugene Wolfgang Positive comments on Gary Kleck & Marc Gertz work
1996, 1997, 1998 CDC (Centers for Disease Control and Prevention) Estimated 1-3 million DGU cases;
But didn’t publish results
1997 David Hemenway Survey Research and Self-Defense Gun Use: An Explanation of Extreme Overestimates;
Criticism on Gary Kleck & Marc Gertz work
1997 Philip J. Cook, Jens Ludwig and David Hemenway The Gun Debate’s New Mythical Number: How Many Defensive Uses Per Year?;
Criticism on Gary Kleck & Marc Gertz work
1997 David Hemenway The Myth of Millions of Annual Self-Defense Gun Uses;
Criticism on Gary Kleck & Marc Gertz work
1997 McDowall and Wiersema The incidence of defensive firearm use by US crime victims, 1987 through 1990.;
Criticism on Gary Kleck & Marc Gertz work
1998 Gary Kleck Degrading Scientific Standards to Get the Defensive Gun Use Estimate Down;
A response to critics
1998 David Hemenway A response to Gary Kleck’s “Degrading Scientific Standards to Get the Defensive Gun Use Estimate Down”
2000 D Hemenway, D Azrael, M Miller Gun use in the United States: results from two national surveys;
Criminal gun use happens much more frequent than DGU.
2014 – 2018 Gun VIolence Archive Verified DGU ranging from 1,383 – 2,115
2015 Evan DeFilippis and Devin Hughes The Myth Behind Defensive Gun Ownership;
Criticism, repeating David Hemenway in 1997
2015 Gary Kleck Defensive Gun Use Is Not a Myth
A response to Evan DeFilippis and Devin Hughes
2018 Gary Kleck How the Hemenway Surveys Distorted Estimates of Defensive Gun Use Frequency
A response to David Hemenway’s “Gun use in the United States: results from two national surveys”


The Pre-1995 of Gary Kleck & Marc Gertz’s Study


There were at least 14 research with estimated annual DGU ranging from 80,000 to 3,609,682.

Source : https://scholarlycommons.law.northwestern.edu/cgi/viewcontent.cgi?article=6853&context=jclc

Prior to 1993, there were at least 14 research involving DGU at the time. Some were primarily devoted to this subject, while others were general purpose opinion surveys which happened to include some questions pertaining to guns.

Sponsors also differed; some were supported by gun-control organizations (Cambridge Reports, Hart), others were supported by gun-freedom organizations (DMIa, DMIb), while still others were paid for by news media organizations, governments, or by research grants awarded to independent academics.

Estimated annual DGU ranges from 764,000 to 3,609,682. With the exception of NCVS (National Crime Victimization Survey), yielding significantly lower estimate of only 80,000 annual DGU cases (Lower than 1/9 the lowest of peer research).

These research also pointed out that victims who resist by using guns are substantially less likely to be injured than victims who do not.

Why prior research were not satisfying?

Gun pointed at a scared Belgian Shepherd's head
Some research included defense against animals.

According Gary Kleck, all these research are not well-suited to determined the number of DGUs. For example, some research did not exclude the DGU against animals, occupational gun use (police force or security guard) while some research included only handguns into the equation.

Furthermore, most surveys did not ask enough questions to establish exactly what was done with the guns in order to confirm the meaningfulness of each DGU case. For example, Respondents might be remembering occasions on which they merely carried a gun for protection ‘just in case’ or investigated a suspicious noise in their backyard, only to find nothing.

Why there was a stark discrepancies between NCVS and other research DGU?

Dr. Gary Kleck pointed out that the NCVS estimate is likely too low due to :

    Faceless person portrait
    Respondents do not have anonymity protection

  1. Respondents do not have anonymity protection. Personal data such as names, addresses are collected.
  2. In 1992, only 4% of people had carry permits, meaning most people’s DGU act outside one’s home was unlawful. (88% of the violent crimes which Rs reported to NCVS interviewers in 1992 were committed away from the victim’s home).
  3. NCVS is conducted by Federal Government, which could deter some people describing their illegal DGU activities.
  4. DGU questions weren’t asked if the participant wasn’t a victim (such as the case where Respondents successfully thwart an assault).
  5. DGU questions were phrase in a general form about whether they did anything to protect themselves rather than directly ask about DGU, making it easier for Respondents to omit the gun defensive part.


1995 – Gary Kleck & Marc Gertz – “Armed Resistance to Crime: The Prevalence and Nature of Self-Defense with a Gun” (Also called NSDS or “National Self-Defense Survey”)


Gary Kleck & Marc Gertz estimated annual DGU ranging from 2.2 – 2.5 million cases.

Source : https://scholarlycommons.law.northwestern.edu/cgi/viewcontent.cgi?article=6853&context=jclc

Dr. Gary Kleck & Dr. Marc Gertz conducted his own research on DGU during February through April of 1993.


His team interviewed a large nationally representative sample (4977 samples) covering all adults, age 18 and over, in the lower 48 states living in households through telephones.

Sampling was randomized (anonymous random digit dialed telephone survey) and stratified by state. This strategy should prevent clustering of cases or multistage sampling.

A phone being used
Anonymous random digit dialed telephone survey

To gain a larger raw number of sample DGU cases, they oversampled in the south and west regions, where gun ownership was higher. And also oversampled males, who are more likely to own guns and might use guns defensively. Data were later weighted to adjust for oversampling.

The details of DGU within 1 year and 5 years period were collected.

Survey questions were carefully crafted to specifically inquire about the detailed events of DGU, such that they had enough information to determine the genuity of DGUs :

  1. The incident involved defensive action against a human rather than an animal, but not in connection with police, military, or security guard duties.
  2. The incident involved actual contact with a person, rather than merely investigating suspicious circumstances, etc.
  3. Defender could state a specific crime which he thought was being committed at the time of the incident.
  4. Gun was actually used in some way. At a minimum it had to be used as part of a threat against a person, either by verbally referring to the gun (e.g., “get away-I’ve got a gun”) or by pointing it at an adversary.

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DGU Results (1993) – Gary Kleck & Marc Gertz

Upper Bound Lower Bound
Total Sample size 4,977 4,977
Weighted annual DGU Cases Upper Bound 66 56
% DGU 1.326 1.125
estimated U.S. Population, April 1993 192,282,775 192,282,775
Implied DGU 2,549,862 2,163,519

Other interesting notes of Gary Kleck & Marc Gertz’s study

Why the DGU estimate might still be too low

  1. It is also probable that typical survey Rs (Respondents) are more reluctant to tell interviewers about questionable acts that they themselves have committed, such as threatening another person with a gun for purportedly defensive reasons.
  2. Few Rs were willing to report a DGU of other member of their household as 85% of the reported of DGUs obtained involved the original Rs.
    (It’s quite unreasonable to assume that the person who answered the phone would consistently turn out to be the individual who had been involved in the DGU.)
  3. Unlike the NCVS, the survey did not cover adolescents, the age group most frequently victimized in violence.
  4. The use of telephone surveying excludes the 5% of the nation’s households without telephones, households which are disproportionately poor and/or rural.
    (Low income persons are more likely to be crime victims, while rural persons are more likely to own guns and to be geographically distant from the nearest police officer.)
  5. Among the sample cases, the offenders were strangers to the defender in nearly 3/4 of the incidents. This reflects the effects of sample censoring.
    Just as the NCVS appears to detect less than 1/10 of domestic violence incidents, Gary Kleck’s survey is probably missing many cases of DGU against family members and other intimates.
  6. Overestimation

  7. A significant source of overestimation of DGUs in this survey is “telescoping,” the tendency of Rs to report incidents which actually happened earlier than the recall period (such as reporting a six year old incident as having happened in the past five years).
  8. Interesting Behavioral Findings

  9. Repeat DGU experiences were not uncommon. 29.5% of DGU-involved households reporting more than one DGU within the previous five years.
  10. Neither the defender/victim nor the criminal ordinarily has much incentive to report this sort of event to the police.
  11. Police interrogation room
    Criminals would not report their own crimes to the police.
  12. Only 24% of the gun defenders in the present study reported firing the gun (including warning shots). 15.6% fired at the offender, and only 8% report wounding an adversary.
  13. Low as it is, even an 8% wounding rate is probably too high. It is suspected that some Respondents “remembered with favor” their marksmanship and assumed they had hit their adversaries. If 8.3% really hit their adversaries, and a total of 15.6% fired at their adversaries, this would imply a 53% (8.3/15.6) “incident hit rate,” a level of combat marksmanship far exceeding that typically observed even among police officers.
  14. Crime victims who use this form of self-protection rarely lose property and rarely provoke the offender into hurting them. In property crime incidents where burglary, robbery, or other thefts were attempted, victims lost property in just 11% of the cases. And gun defenders were injured in just 5.5% of all DGU incidents.
  15. Although the gun defenders usually faced unarmed offenders or offenders with lesser weapons, they were more likely than other victims to face gun-armed criminals.
  16. Victims who used guns faced multiple offenders in 53% of the incidents, compared to just 24% of overall victims facing multiple offenders.
  17. Multiple offenders and guns
    Multiple offenders and guns
  18. Only 3% of all the incidents involved both parties shooting at each other.
  19. 15.7% of the DGU Respondents stated that they or someone else “almost certainly would have” been killed, with another 14.2% responding “probably would have” and 16.2% responding “might have.” 96 Thus, nearly half claimed that they perceived some significant chance of someone being killed in the incident if they had not used a gun defensively.

    If this 15.7% were to be applied to the estimated DGU, it means that 340,000 to 400,000 DGUs would believed they almost certainly had saved a life by using the gun.

    *These are just stated perceptions of Respondents, not objective assessments of actual probabilities.
  20. A disproportionate share of defenders are African-American or Hispanic. Additionally, defenders are disproportionately likely to reside in big cities and likely to be single. On the other hand, defenders are not likely to be poor.
  21. Other

  22. The sample size of this study (4,977) is large enough that random sampling error with 95% confidence interval is +-0.32%
  23. The health system cannot shed much light on this phenomenon, since very few of these incidents involve injuries. In the rare case where someone is hurt, it is usually the criminal, who is unlikely to seek medical attention for any but the most life-threatening gunshot wounds
  24. As a point of comparison, the largest number of deaths involving guns, including homicides, suicides, and accidental deaths in any one year in U.S. history was 38,323 in 1991.
  25. Suppose someone persisted in believing in the NCVS estimates of DGU frequency and wanted to use a “dishonest respondent” hypothesis to account for estimates from the Gary Kleck & Marc Gertz’s survey that are as much as 30 times higher.
    A man holding fingers crossed behind his back
    Extreme lying responses

    One would have to suppose that 29 out of every 30 people reporting a DGU in the present survey were lying. There is no precedent in criminological survey research for such an enormous level of intentional and sustained falsification.

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1995 – Marvin Eugene Wolfgang – Positive comments on Gary Kleck & Marc Gertz work

Source :

  1. https://en.wikipedia.org/wiki/Marvin_Wolfgang
  2. https://scienceblogs.com/deltoid/1996/12/16/dgu-00026
  3. https://scholarlycommons.law.northwestern.edu/cgi/viewcontent.cgi?httpsredir=1&article=6854&context=jclc

Marvin Wolfgang, a known criminologist who doesn’t support guns for defensive use, was even impressed with the research methodology done by Gary Kleck and Marc Gertz. But he did point out that the sample size (4,977) was relatively small compared to extrapolated U.S. population.


1996, 1997, 1998 – CDC (Centers for Disease Control and Prevention)

Source :

  1. https://www.forbes.com/sites/paulhsieh/2018/04/30/that-time-the-cdc-asked-about-defensive-gun-uses/
  2. https://capitalresearch.org/article/why-is-the-cdc-hiding-its-defensive-gun-use-statistics/
  3. https://reason.com/blog/2018/04/20/cdc-provides-more-evidence-that-plenty-o

The CDC conducted their own DGU studies in 1996, 1997 and 1998. They have estimated annual DGU of 1-3 million cases but didn’t publish their results.


1997 – David Hemenway – “Survey Research and Self-Defense Gun Use: An Explanation of Extreme Overestimates”


G-K’s (Gary Kleck & Marc Gertz) paper is faulty due to (1) Small sample size (2) Estimating very rare events (3) Invalid external validity check

Source : https://scholarlycommons.law.northwestern.edu/cgi/viewcontent.cgi?article=6936&context=jclc

David Hemenway, Professor of Health Policy at the Harvard School of Public Health, argued that Gary Kleck & Marc Gertz’s DGU estimate is not accurate. Here are his arguments.

1. Respondents likely exaggerated about their DGUs

Since it’s natural for people to present themselves in a positive way, David Hemenway reasoned that an individual who purchases a gun for self-defense and then uses it successfully to ward off a criminal is displaying the wisdom of his precautions and his capability in protecting himself, his loved ones, and his property.

2. Problems with estimation of “very rare events”

Since no survey is ever perfect. Some percentage of answers to virtually all survey questions are incorrect. Respondents substantially over-report their seat belt use, for example, and inaccurately report whether they voted.

Suppose that there is just 1% error from the whole sample, mistakenly categorizing non-DGU to DGU. And suppose that the estimated DGU is 1.1% (with 1% wrong), thus the true DGU is only 0.1% or less than 1/10 of the estimated DGU.

On the other hand, a 1% error on the other side, estimated Non-DGU of 98.9% (with 1% error) would mean that the true Non-DGU is 99.9% or very slight discrepancy percentage wise.

Thus it is very likely that the survey finding will be an overestimation.

3. Small Sample Size

Coupled “very rare events” with small sample size (4,977) relative to U.S. population, and you get extreme overestimates.

There are 8 other survey at the time, however, even if all these private surveys were combined, including the K-G survey, they would not be half the size of a single NCVS survey.

An analogy

Consider the responses to a national random-digit-dial telephone survey of over 1500 adults conducted in May 1994 by ABC News and the Washington Post.

One question asked: “Have you yourself ever seen anything that you believe was a spacecraft from another planet?”

10% of respondents answered in the affirmative. These 150 individuals were then asked, “Have you personally ever been in contact with aliens from another planet or not?” and 6% answered ‘Yes.”

2 aliens with space and earth background
Almost 20 million people met these?

By extrapolating to the national population, we might conclude that almost 20 million Americans have seen spacecraft from another planet, and over a million have been in personal contact with aliens from other planets.

4. External Validity Check

Various checks for external validity of the Kleck-Gertz finding confirm that their estimate is highly exaggerated.

4.1 External Validity : Burglaries

K-G find that 34% of the time a gun was used in self defense, the offender was committing a burglary. If we use their 2.5 million estimate, we would conclude that, in 1992, DGU happened in approximately 845,000 burglaries.

However, from the NCVS, we know that there were fewer than 6 million burglaries in 1992. Over 55% of the time the residence was definitely unoccupied at the time of the burglary (in another 23% it was not known whether the dwellings was occupied or not). Only 22% of the time was someone certainly at home (1.3 million burglaries).

Kleck accepts as valid the claim that the dwellings were occupied in only 9% of U.S. burglaries. Since fewer than half of U.S. households have a firearm of any kind and since the victims in 2/3 of occupied dwelling were asleep, the K-G result asks us to believe that burglary victims in gun owning households use their guns in self-defense more than 100% of the time, even though most were initially asleep.

Additional Atlanta Police Department Data

Examining a 3 month period in 1994 of Atlanta police department home invasion crime reports, researchers identified 198 cases of unwanted entry into a single-family dwelling while one or more individuals were present in the home.

In 16% of the cases of home invasion, at least one of the offenders carried a firearm. In only three cases (1.5%) was a victim able to use a firearm in self-defense.

To accept the K-G results requires a belief that, of the 198 events, all the families with guns actually used them in self defense, but only three bothered to tell the police.

4.2 External Validity : Gun Shot Wounds

K-G report that 207,000 times per year the gun defender thought he wounded or killed the offender.57 However, only about 100,000 people are treated in emergency rooms each year for non-fatal firearm-related injuries; 58 almost all of these are victims of assault, suicide attempts and unintentional gun shootings rather than criminals shot by defenders.

Military medic binding gunshot wound during fight
Not enough gunshot wounds

4.3 External Validity : Murders

K-G report that 392,000 times per year a gun defender thought that someone almost certainly would have been killed had the gun not been used; that another 355,000 times someone probably would have been killed; and another 405,000 times someone might have been killed if the gun had not been used for protection.

The K-G results imply that many hundreds of thousands of murders should have been occurring when a private gun was not available for protection. Yet guns are rarely carried, less than a third of adult Americans personally own guns, and only 27,000 homicides occurred in 1992.

Given the number of victims allegedly being saved with guns, it would seem natural to conclude that owning a gun substantially reduces your chances of being murdered. Yet a careful case-control study of homicide in the home found that a gun in the home was associated with an increased rather than a reduced risk of homicide.

4.4 External Validity : Criminals being outgunned

The 2.5 million figure would lead us to conclude that, in a serious crime, the victim is three to four times more likely than the offender to have and use a gun.

Although the criminal determines when and where a crime occurs, although pro-gun advocates claim that criminals can always get guns, although few potential victims carry guns away from home, the criminal, according to K-G, is usually outgunned by the individual he is trying to assault, burglarize, rob or rape.

K-G’s explanation is nonsensical : “(This) should not come as a surprise, given that there are far more gun-owning crime victims than there are gun-owning criminals and that victimization is spread out over many different victims, while offending is more concentrated among a relatively small number of offenders.”

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5. Survey Could Be Rigged

The survey was conducted by a small firm run by Professor Gertz. The interviewers presumably knew both the purpose of the survey and the staked-out position of the principal investigator regarding the expected results.

A man is cheating with a graph presentation
Hmm, this bar is definitely too low …

6. Unexplained Methodology

6.1 Unanswered Calls

The G-K study states that when a person answered, the interview was completed, which was 61% of the time. But what happened when there was a busy signal, an answering machine or no answer? If no one was interviewed at a high percentage of the initially selected homes, the survey cannot be relied on to yield results representative of the population.

6.2 Weighting Issues

K-G oversampled males and individuals from the South and West. The reader is presented with weighted rather than actual data, yet the authors do not explain their weighting technique.

They claim their weighted data provide representative information for the entire country, but they appear to have obtained various anomalous results. For example, they find that only 38% of households in the nation possess a gun, which is low, outside the range of all other national surveys. They find that only 8.9% of the adult population is black, when 1992 Census data indicate that 12.5% of individuals were black.

7. Selective Male Head of the Household Respondent

Interviewers do not appear to have questioned a random individual at a given telephone number, but rather asked to speak to the male head of the household. If that man was not at home, the caller interviewed the adult who answered the phone. Although this approach is sometimes used in telephone surveys to reduce expense, it does not yield a representative sample of the population.

8. Strategic Reporting

Some respondents were undoubtedly aware of the debate over the incidence and utility of gun use in self-defense. A few might actually deliberately lie on a telephone survey to help boost the numbers for the sake of their political beliefs concerning the dangers of gun control.

9. Telescoping

False positives can also come from external “telescoping,” the reporting of events that actually occurred, but were outside the time frame in question.

A Table to Illustrate the Small Sample Size & Very Rare Events Problem

Screen: Response to Self-Defense Gun Gun Use Question Positive (Truth) : A Self-Defense Gun Use Negative (Truth) : No Self- Defense Gun Use Total
Positive 16 50 66
Negative 0 (actually 0.16) 4,934 4,934
Total 16 4,984 5,000

Assumptions :

  • 66/5,000 screens report a positive finding
  • Test Sensitivity: 99%
  • Test Specificity: 99%

(Or a random 1% of respondents are misclassified)

Summary :

  • Predicted Incidence: 66/5000 = 1.33
  • True Incidence: 17/5000 = 0.32
  • Survey Overestimation: 4 times too high
  • Estimated total Defensive Gun Use: 2.5 million
  • True total Defensive Gun Use: 0.6 million

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1997 – Other Gary Kleck’s Critics that May Interest You


1998 – Gary Kleck’s Response to Critics – “Degrading Scientific Standards to Get the Defensive Gun Use Estimate Down”


Critics provided no empirical data to back up their speculations. And they rely only on NCVS data to check external validity of G-K’s work, which is not practical as the NCVS survey doesn’t have all the data on every crimes in United States.

Source : https://www.saf.org/wp-content/uploads/journals/JFPP11.pdf

Here are Gary Kleck’s comments on the critics :

1. One is more than many?

Oppositions based their conclusion entirely on a single survey, the NCVS (National Crime Victimization Survey), which did not even directly ask respondents about defensive gun use. It missed approximately 97% of rapes and sexual assaults, and over 90% of spousal assaults (p. 168, citing the review by Loftin and MacKenzie 1990).

A red sphere outweigh a stack of dark gray spheres
That’s one heavy ball.

Tom Smith, Director of the National Opinion Research Center, has noted, specifically in connection with the NCVS: “Indirect questions that rely on a respondent volunteering a specific element as part of a broad and unfocused inquiry uniformly lead to undercounts of the particular of interest” (Smith 1997, pp. 1462-1463).

Critics to G-K got around large volume of contrary survey evidence by pronouncing all of them invalid.

2. Speculation Beats Empirical Evidence?

Oppositions almost entirely depended on one-sided speculation about errors in surveys that supposedly cause overestimation of DGUs, without any empirical evidence. For example :

2.1 Respondents Misinterpret DGU

  • Reiss and Roth speculated that many respondents so radically misunderstood the question pertaining to defensive uses of guns that they reported incidents in which they merely “brought the gun nearby in anticipation of an encounter that never occurred” (p. 265).
  • McDowall speculated that respondents might have thought that merely carrying a gun for protection constituted actually using it for self defense (1995, p. 137).
  • Hemenway speculated that respondents might have reported incidents “in which they were afraid, they retrieved a gun, and nothing bad happened.”
  • Kleck and Gertz (1995) tested these speculations and found little support for them––respondents claiming a DGU nearly all directly confronted their adversaries and, at minimum, pointed their guns at them or referred to the guns verbally in a threatening manner. No more than 13 of 222 cases (6%) initially reported as DGUs were “no-encounter” cases of the sort imagined by Reiss and Roth or by McDowall.

2.2 Respondents Mentally ill

Mentally ill man in strait-jacket in room corner
Many Rs were like this?

Hemenway speculated that people claiming DGU experiences might have been mentally ill, inventing nonexistent DGUs, due to their “different perception of reality” (p. 1435).

He did not provide any evidence that even one of the DGU-reporting respondents in the NSDS or any of the other DGU survey was in fact mentally ill. Nor did he explain why the “different perception of reality” of mentally ill people would cause them to develop long, detailed, and internally consistent accounts of nonexistent DGUs.

2.3 Respondents Deliberately Lying

Hemenway also speculated that respondents reporting DGUs were deliberately lying for the explicit purpose of boosting DGU estimates, in order to advance their political beliefs opposing gun control. But again is devoid of any empirical evidence.

An honest misunderstanding of real events in a way that would falsely qualify them as DGUs is more plausible such as those where people prefer to characterize their partly aggressive, partly defensive behavior in “mutual combat”. But Kleck and Gertz addressed this possibility in their original article and showed that it could not account for more than a small fraction (probably less than 1/10) of the incidents they counted as DGUs (1995, p. 174)

2.4 Deliberately Lying G-K

Hemenway wrote: “the survey was conducted by a small firm run by Professor Gertz. The interviewers knew both the purpose of the survey and the staked-out position of the principal investigator regarding the expected results”.

To our knowledge, none of the interviewers knew anything about Kleck’s views on DGU or what results he expected, since Kleck did not inform them of those views.

Hemenway did not claim to have communicated with even one of the interviewers, to find out what they knew prior to interviewing. Therefore, he had no basis whatsoever for this outrageous charge.

2.5 Criminals are more likely than victims to possess guns

Hemenway argued that “criminals are more rather than less likely than victims to possess guns” (1997b, p. 1443), but offered no supporting evidence.

In 1991, only 24% of state prison inmates personally owned a gun in the month before they were arrested for the offense that got them sent to prison (U.S. Bureau of Justice Statistics 1993, p. 19), while the 1989 General Social Survey indicated that 31% of the general U.S. adult population personally owns a gun (Kleck 1991, p. 52).

Furthermore, NSDS (G-K’s work) indicated that each year over 7 million U.S. adults carry guns on their person for self-protection for an average of 138 days per year, implying nearly one billion person-days of such carrying (Kleck and Gertz 1998), compared to 0.7-1.6 million DGUs in public places (Kleck and Gertz 1995).

2.6 The Number Game

Regarding Hemenway’s table where he arbitrarily assumes particular rates of false positives and false negatives, along with extremely low actual DGU rates (instead of using the empirically-based 1.33% estimate Kleck and Gertz obtained, Hemenway assumed imaginary DGU rates of 0.32%, 0.04% and 0.08%, respectively), if there were any credibility to the misreporting rates that he assumed out of thin air, they would indeed imply huge overestimates.

But he presents no empirical evidence to support his claim.

3. About Atlanta Police Data

In David Hemenway’s argument, there was a mention to a study by Kellermann where he assessed the frequency of DGUs linked with home invasion crimes entirely on the basis of the number of times victims volunteered information about such DGUs to Atlanta police.

According to the Atlanta Police Department, the offense report forms do not include a box or other place calling for information about victim weapon use, nor are officers trained or required to ask crime victims about such things.

Thus, information about victim weapon use, no matter how common it might in fact be, would almost never appear in police offense reports (a fact reported in the journal that published the Kellermann article).

4. Telescoping VS Recall Failure

Regarding telescoping issue (respondents reporting events as having happened during the recall period, though they actually occurred earlier), while some respondents undoubtedly do telescope DGUs into the recall period, this error would not lead to an overestimate of DGU incidence unless the effects of telescoping exceeded the effects of recall failure, i.e. respondents forgetting or intentionally failing to report genuine DGUs.

The relevant technical literature indicates that the relative size of recall failure effects (mostly forgetting) compared to telescoping effects grows with increasingly long recall periods, moving estimates in the direction of a net undercount (Sudman and Bradburn 1973; Woltman, Bushery and Carstensen 1984).

And recall failure and telescoping effects appear to be about equal in surveys of crime victimization with a one year recall period (Dodge 1970).

Cook offered no evidence that any DGU surveys or indeed any crime-related surveys, are afflicted by more telescoping than recall failure.

Furthermore, direct evidence from Census Bureau research (on the NCVS) reveal that surveys of crime victimization have about 21% telescoping rate. And it is absurd to suggest that 21% telescoping rate could account for more than a negligible share of, for example, the 30-to-1 difference between the NSDS and NCVS estimates.

On the other hand, it is a simple matter to attribute the enormous discrepancy to radical

underreporting in the NCVS, since there is already ample evidence of similarly radical underreporting of other violence related events in this survey, including domestic violence, rapes, and gunshot woundings linked with criminal assaults (Cook 1986; Loftin and MacKenzie 1990).

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5. Up VS Down

Even if some critics’ speculations about flaws in DGU surveys had been correct and consequential, it is not helpful or honest to speculate only in one direction, such as speculating only about flaws that might artificially push DGU estimates up. One must also consider other flaws that can also push DGU estimates down. Such as :

  • Telescoping VS. Recall failure
  • False positives (respondents claim DGU to appear heroic) VS. False negatives (respondents concealing or forgetting DGUs)

6. UFO & DGU

An analogy to the mentioned UFO case (from David Hemenway), the reason most people do not share beliefs about UFOs is not that the beliefs can be proven false (since it is impossible to prove a negative). Rather, most people reject them because there is no credible evidence that they are true.

It is the same with speculations about DGU surveys’ supposed flaws. Since it is impossible to prove a negative, one cannot prove that massive misreporting of nonexistent DGU incidents does not occur in surveys. There is, however, no evidence whatsoever that such massive misreporting does occur.

And unlike respondents in the UFO survey, NSDS respondents who wanted to falsely report a nonexistent DGU could not qualify as having had such an experience merely by saying “Yes.”

Rather, they had to provide as many as 19 internally consistent responses covering the details of the alleged incident. In short, to sustain a false DGU claim, respondents had to do a good deal of very agile mental work, and stay on the phone even longer than just responding “No”.

7. Medical Validity

Medical and DGUs numbers are consistent with each other.

Fatal gun shots
Fatal gun shots

Apart from the most life-threatening of Gun Shot Wounds (GSW), criminals are unlikely to seek medical treatment, since medical personnel are required to report gunshot wounds to police. Most GSW are survivable without professional medical treatment (Kleck 1997, Chapter 1).

8. Crime Validity

Many opposition claimed that estimated number of DGUs connected with particular types of crimes were inconsistent with NCVS estimates of the total number of crimes of a given type, with or without DGUs.

This had already been anticipated in a passage in the original article reporting the NSDS estimates (Kleck and Gertz 1995, pp. 167-168) : “a large share of the incidents covered by our survey are probably outside the scope of incidents that realistically are likely to be reported to either the NCVS or police”.

Because DGUs typically involve criminal behavior, such as unlawful gun possession, by the gun-using victim, who therefore is often unwilling to report the incident.

9. Hemenway’s Social Desirability Response

Regarding his “Social Desirability Response” theory, Hemenway cited surveys

about height, automobile ownership, diseases, and other topics of negligible similarity to the topic at hand, he said nothing about evidence concerning the validity of responses to questions requiring respondents to report their own illegal behavior.

A large body of empirical evidence indicates that, when asked questions about their own illegal behavior, survey respondents, on net, underreport their involvement. And false negatives outnumber false positives by a wide margin.

The strongest tests of validity on such questions concern illicit drug use. For example, among patients at a walk-in clinic who had positive urine tests for illicit drug use, only 28% had admitted the use in interviews (McNagny and Parker 1992), i.e. actual use was 3.6 times higher (100/28=3.6) than reported use.

It is unfortunate there is no way to estimate false positives and false negatives as authoritatively with DGUs as with illicit drug use. We are forced to make do with validity checks on surveys addressing other experiences analogous to DGU.

10. A Large National Survey Supports K-G Results

Another large-sample national survey, sponsored by the National Institute of Justice (NIJ), conducted under the auspices of the Police Foundation, strongly confirmed G-K’s DGU findings.

Kleck, the principle consultant on the Police Foundation survey, wrote most of the associated grant proposal and most of the questionnaire, and participated in numerous meetings with Hemenway and Cook.

It constituted about as strong an external validity check as one could ask for.
Bullshit stamp

When the Police Foundation survey almost exactly confirmed the NSDS results, Hemenway’s response was to suddenly decide that surveys inevitably overstate DGU frequency.

Note that Hemenway also served on the NIJ Advisory Committee for the project and was thanked for his comments on a draft of the grant report describing the survey’s findings, including its DGU estimates (Cook and Ludwig 1997, p.x).

He had ample opportunity to suggest solutions to problems he saw in this survey, or to suggest other steps “to reduce the bias or to validate the findings by external measures,” and to show that DGUs are really far less common than so many surveys have indicated.

But he didn’t, nor did he mention this NIJ survey in his arguments.

11. Did Hemenway say G-K’s DGU was too low?

Hemenway made many claims that could be implied as too low DGU in G-K study. He said that G-K’s work has :

  • Too low estimate of gun ownership prevalence in their sample : Since DGUs are obviously more common among gun owners, any underrepresentation of gun owners in the survey sample would contribute to an underestimate of DGUs.
  • Underrepresentation of blacks sample : By underrepresenting highly victimized subsets of the population, the survey would necessarily imply an underrepresentation of persons who had occasion to engage in acts of self-defense, including use of a gun for self protection.
  • Too much weight to persons who are the only adult in their household : According to “U.S. Bureau of Justice Statistics 1996, p. 28”, persons who live alone or in smaller households are less likely than others to be victims of crimes like burglaries, thus likely to contribute to an underestimation of DGUs.

12. Some Interesting Factors Hemenway Left Out

  • Surveys confined to adults would exclude all self-reports of DGU by adolescents. Since rates of gun carrying are as high among adolescents as among adults (Kleck and Gertz 1998, pp. 200-201), and persons age 12-17 claim about 24% of all violent victimizations (U.S. Bureau of Justice Statistics 1997, pp. 6, 8), this problem alone could cause surveys to miss as much as a quarter of all DGUs.
  • Omission of persons without telephones, who are poorer and thus more likely to be crime victims than others, would be another source for underestimation of DGUs.

13. Some Irrelevant Arguments

Some argument, while colorful, are irrelevant. Such as the one saying “Gun in the home raises the risk of homicide”. This is unrelated to DGU number.

14. Regarding Unexplained Methodology

Regarding the absence of details on methods for weighting data and survey organization procedures for handling busy signals or answering machines, these things are extremely specialized technical matters that most surveys do not report including Hemenway et al. 1995; Hemenway and Richardson 1997, pp. 188-190; Weil and Hemenway 1992; 1993a.

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Furthemore, the criticism was so devoid of content that Hemenway did not even bother saying why any of these hypothetical problems, even if they had existed, would have caused the DGU estimate to be too high.

15. Some More Surveys Supporting G-K Results

The more technically sound the surveys became, the larger the DGUs estimates got (compare Cook and Ludwig 1997 and Kleck and Gertz 1995 with the pre-1991 surveys critiqued in Reiss and Roth 1993, and summarized in Kleck 1997, pp. 187-189).

Thus, G-K DGU number is even more confirmed.

16. The Tricky Relation Between David Hemenway and NCVS

Hemenway never explicitly stated that he considered the NCVS estimates to be even approximately accurate, perhaps because he knew that this position was indefensible.

He made no effort to rebut Kleck and Gertz’s detailed explanation (1995, pp. 153-157) of why the NCVS grossly underestimates DGU frequency, and did not even discuss or mention most of their arguments or evidence.

17. G-K’s Sample Size

Hemenway’s logic was also fallacious in assuming that one can cast doubt on conclusions based on a large body of data by deriving implausible implications from smaller subsets of the data.

The NSDS estimates of total DGUs are likely to be fairly reliable partly because they are based on a very large (n=4,977) sample, while any estimates one might derive pertaining to one specific crime type are necessarily less reliable because they rely partly on a far smaller subsample, i.e. the c. 194 sample DGU cases, of which 40 were linked to burglaries.

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1998 – David Hemenway’s response to Gary Kleck


Super sensitive results for very rare event is real. Medical attention for gunshot wounds is real. G-K’s work doesn’t pass external validity check. NCVS is the most sophisticated survey. And empirical evidence is not needed to debunk this DGU myth.

Source : http://www.hsph.harvard.edu/wp-content/uploads/sites/1264/2013/09/Response-to-Kleck-SDGU.docx

Here are David Hemenway’s response to Gary Kleck’s “Degrading Scientific Standards to Get the Defensive Gun Use Estimate Down” :

1. G-K’s Survey Problems are Real

Kleck argues that the sole aim of my article was political, to serve “the narrow political purpose of ‘getting the estimate down’ for the sake of advancing the gun control cause,”.

The goal of D. Hemenway’s article was to bring more science into firearm scholarship.  The serious problem of false positives when estimating rare events has not been sufficiently recognized in survey research (Hemenway, “The Myth of Millions of Annual Self-Defense Gun Uses: A Case Study of Survey Overestimates of Rare Events” Chance 1997; 10:6-10).

Drawings related to science
The more Science, the better

Many specific problems exist with the Kleck-Gertz survey (e.g. the surveyors tried to speak to the male head of the household, which does not yield a representative sample of the population;  the survey is randomized by dwelling unit, but the extrapolation is by individuals, etc).

Yet Kleck & Gertz never discuss many of the methodological issues or limitations of their survey, in either their original article or in their rebuttal.

2. NIJ Survey Stance

Kleck reported “Hemenway does not mention the results of this [National Institute of Justice] survey, perhaps for an understandable reason: It almost exactly confirms our results…”.

The truth is, I did not discuss that survey because when I submitted my article in early 1996, even preliminary results were not yet available.

One reason it took so long for my article to be published (it was published in early 1998, with no substantive changes) was the time it took for Kleck to write his rebuttal and because, I was told, that he threatened to sue the Journal of Criminal Law and Criminology for libel if they published my article.

It should be noted that the conclusions of NIJ report are in complete disagreement with Kleck concerning his claims about self-defense gun use (Cook P, Ludwig J.  Guns in America. National Institute of Justice Report, 1997).

3. Not Lying but Inadequate Handling

Hemenway wrote:  “For example, the survey was conducted by a small firm run by Professor Gertz.  The interviewers presumably knew the purpose of the survey and the staked-out position of the principal investigator regarding the expected results” (p. 1433).

The issue, of course, is not one of deliberate falsification, but one of “blinding.”

Good science requires that individuals collecting information be blinded to the expected or hoped-for results of the investigation, to eliminate the possibility of subtle bias.

Kleck’s position on self-defense gun use was well known. In the Kleck-Gertz paper, we have the unusual instance of the head of the independent survey firm which did the interviewing being both from the same school (Florida State) as the principal investigator and being co-author of the resulting publication.  The survey instrument was entitled “National Self-Defense Survey,” and the surveyors began with a “Hello, my name is ___ with Florida State University.”

4. Rare Event Sensitivity

Regarding the sensitivity of DGU results with false positives (respondants falsely reported DGU cases), there is no question but that the Kleck-Gertz results are extremely sensitive to small changes in the specificity rate.

Since all surveys have some misclassification, David Hemenway examined what the true rate of self-defense gun use would be under various assumptions about the specificity and sensitivity rates. Under most reasonable assumptions, their 2.5 million is a wild overestimate.

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5. False Positives VS False Negatives

Social Desirability Bias

The social desirability bias doesn’t have to be predominant for most people. Given the rare nature of the event, it just has to be predominant for some small percentage of respondents.

All available evidence indicates that self-defense gun use is perceived by most people as beneficial, socially desirable and often heroic.

For example, in the Kleck-Gertz survey, over 46% of respondents claim that their gun use might have saved–or probably would have saved, or almost certainly did save–someone from dying.  Saving someone from death seems pretty heroic.

If their respondents’ claims are correct, over 1 million murders a year may have been directly prevented by self-defense gun use (yet there were only 27,000 total murders in 1994). Also note that Kleck’s self-defense gun users are almost always defending themselves against serious crimes.

The Illegality of Self-Defense Gun Use

Kleck offers no evidence about the legality of the self-defense gun use.

If illegal, it would be the possession, or carrying, or actual use that was illegal. Yet Kleck and Gertz oversample men, in the West and the South, where gun household gun ownership is over 50%, and both ownership and carrying laws are quite permissive.

Who then, are these individuals who can’t legally obtain guns and/or carry them?

If Kleck is right about the illegality, most of his so-called self-defense gun use may be detrimental to society.

Also Kleck claimed that asking about self-defense gun use is equivalent to “requiring respondents to report their own illegal behavior.” But tens of millions of Americans own guns legally, millions carry guns legally, tens to possibly hundreds of thousands use guns legally in self-defense.

Admitting to owning or carrying or using a gun admits to nothing about unlawful activity, just as responding that one was the driver in a car crash admits to nothing about illegal behavior.

Respondents were afraid that if they reported an illegal self-defense gun use, they could get into trouble

Not only were respondents not asked to report illegality, but the NCVS and the one-shot interviews have never used any information received to identify or punish any individual’s illegal behavior.

The Census Bureau assures respondents that all information is confidential, and it would be illegal for the interviewers to provide individual information to the authorities;

6. Kleck’s Cited Irrelevant Studies

Kleck claims to present relevant evidence that “self-report studies underestimate illegal behavior.” But all the studies cited by Kleck are irrelevant–they do not deal with rare events for the population studied, and the surveys were conducted on vulnerable individuals, who were asked directly about illegal actions by people who could penalize them.

Gang Of Young Men Taking Drugs Indoors
Gang Of Young Men Taking Drugs Indoors

For example, Kleck cites a study that found among juvenile arrestees, over two thirds of whom tested positive for cocaine, only 23% reported using cocaine in the past 90 days (p. 1149).

Is anyone surprised? Is that finding at all relevant to an anonymous self-report telephone survey of the general population of a rare event (self-defense gun use), an event should generally be legal and has positive social desirability?

Much evidence actually exists which demonstrates that on anonymous telephone interviews people willingly report a large amounts of minor and not-so-minor criminal behavior, even behavior that has little possibility of positive social desirability bias.

For example, in a telephone study of California motorists, 20% reported running a red light in the past month and 8% reported driving after they thought they had too much to drink in the past year (Hemenway D, Solnick SJ.  “Fuzzy Dice, Dream Cars and Indecent Gestures: Correlates of Driver Behavior?” Accident Analysis and Prevention, 1993; 25:161-170).

7. NCVS is a good measurement of crime

Kleck argues, that it impossible to check his 2.5 million figure against any other results (e.g. estimates of crimes, bullet wounds), because no other measure is any good.

Plus, Kleck argues that the NCVS misses many crimes because the victim may have used a gun illegally during the crime, and thus is afraid to report his attempted victimization to interviewers.

In fact, The National Crime Victimization Surveys provide good estimates of serious crime, such as burglary and robbery. As himself Kleck writes:  The NCVS “survey instrument has been carefully refined and evaluated over the years to do as good a job as possible in getting people to report illegal things which other people have done to them”

The NCVS asks first about the crime. It never directly asks about gun use, but only asks what the victim did. The victims do not have to report gun use if they don’t want.

Indeed, Kleck previously claimed (not persuasively) that the overwhelming majority of respondents who used a gun in self-defense deliberately lied to the surveyors about their self-defense gun use. Now he claims that the vast majority don’t even report the incident in the first place.

8. Gun Shot Wounds do not lie

Kleck claims that most people are not treated medically for gunshot wounds. He also claims that only a small percentage of criminals who are wounded ever seek medical attention.

All of the many ER physicians and surgeons are incredulous about the claim, that most or even a sizable percentage of gunshot wound victims do not seek medical treatment.

There is no evidence of large number of cases of infection and sepsis caused by untreated wounds, which would be expected if most people did not seek professional treatment. Kleck as usual provides no evidence for his strange conjecture.

9. Why NCVS gives the best estimates, and not other surveys

One-shot telephone surveys, which typically have one gun self-defense question, do give large estimates of self-defense gun use, ranging from 700,000 to many million of uses per year.

But each National Crime Victimization survey, performed semi-annually or twenty times a decade, give results an order of magnitude lower. Thus every six months a very large and highly sophisticated survey gives completely different results than Kleck’s estimates.

Kleck’s self-defense estimates are therefore not “one of the most consistently supported assertions” in the gun field.  And while the NCVS is far from a perfect measure, because of the false positive problem with rare events, the NCVS undoubtedly provide a more reasonable ballpark estimate than one-shot surveys.

10. Why no empirical data

It is not necessary to present new data to show that a research result is wrong.

An Aboriginese man
This guy is 60 feet tall!

For example, assume that someone was publicly touting that he had found a tribe of aborigines who were 60 feet tall. It would be enough for a scientist to show that the yardstick that was used to measure these aborigines was closer to 3 inches long rather than 3 feet long, so that the natives were probably closer to 5 feet tall rather than the reported 60 feet tall, and to further show that people 60 feet tall would not be able to pump blood to their head.

The truth could not be dismissed by the claim that the scientist had not gone out and measured the natives himself.

11. Contradicting G-K with Peer Review Papers

And many peer review papers’ conclusions are :

  1. Criminal gun use in the United States occurs far more often than self-defense gun use. This result is completely opposite to the incorrect Kleck claim (p. 180), possibly because he did not ask about the use of guns against the respondent.
  1. Self-defense gun use against an animal is more common than self-defense gun use against a person.  This result is also in complete contradiction to the Kleck-Gertz results, probably because they asked about use against an animal only after asking about self-defense gun use generally.
  1. Individuals without guns are not necessarily unarmed. In our survey, more people reported instances of self-defense with a baseball bat than with a gun.
  1. Much reported self-defense gun use is not socially desirable. Although respondents present only one side of a confrontation, an unbiased reading of their self-defense reports indicates that in many cases, the respondent’s gun use was clearly unlawful and anti-social, irrespective of whether the gun possession and carrying were legal.

12. If Kleck is correct …

If Kleck is correct, in serious crimes the victim is 3-4 more likely than the offender to have and to use a gun. Yet the criminal gets to determine when and where the crime occurs.

If Kleck’s numbers are to be believed, decent-law-abiding citizens with guns should be many times safer from homicide than similar individuals without guns. But case-control studies show precisely the opposite.

If Kleck is correct, the National Crime Victimization Survey, the largest, most expensive, most sophisticated self-report survey on victimization in the world, misses most gun use during crimes because respondents deliberately lie to the Bureau of Census interviewers.  Yet respondents largely tell the truth on other surveys conducted by the Census.

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2000 – D Hemenway, D Azrael, M Miller – “Gun use in the United States: results from two national surveys”


A research found that there are far more criminal gun uses than self defense gun uses.

Source : https://injuryprevention.bmj.com/content/injuryprev/6/4/263.full.pdf

1. Methodology

Harvard national random digit dial telephone surveys of the adult population were conducted in 1996 and 1999.

The surveys appear unique among private surveys in two respects: asking (1) open ended questions about defensive gun use incidents and (2) detailed questions about both gun victimization and self defense gun use.

Respondents who answered yes to gun use qualifying question were asked up to 30 follow up questions about the most recent event, including an open ended question which asked them to describe the incident.

All results eliminated respondents who were police officers, security guards, or military personnel.

Results also eliminated cases in which the respondent reported that the event occurred more than five years before the survey or outside the United States.

The Legal Side

Self defense gun use incidents were summarized and sent to 5 criminal court judges (from California, Pennsylvania, and Massachusetts) who were assured anonymity.

Valuing scale
Opinions from the judges

The judges were told to assume that the respondent had a permit to own and carry the gun and had described the event honestly from his/her own perspective.

Then they gave their best guess whether, based on the respondent’s description of the incident, the respondent’s use of the gun was likely legal or unlikely legal.

2. Shocking Conclusion

Even after excluding many reported firearm victimizations, far more survey respondents report having been threatened or intimidated with a gun than having used a gun to protect themselves.

A majority of the reported self defense gun uses may well be illegal (rated by a majority of judges) and against the interests of society. This was so even under the assumption that the respondent had a permit to own and carry the gun, and that the respondent had described the event honestly.


2014 to Present – Gun Violence Archive

Source : https://www.gunviolencearchive.org

Gun Violence Archive provides a database for verified DGUs since 2014 to present. They do not take into account stories not reported nor extrapolations from surveys.

Year Reported DGUs
2014 1,560
2015 1,383
2016 1,996
2017 2,115
2018 1,768


2015 – Evan DeFilippis and Devin Hughes VS Gary Kleck

Source : https://www.politico.com/magazine/story/2015/02/defensive-gun-ownership-gary-kleck-response-115082

Evan DeFilippis and Devin Hughes repeated the issues cited by David Hemenway in 1997. Hearing this, Gary Kleck cited his own response to David Hemenway in 1998.


2018 – Gary Kleck’s Response to D. Hemenway’s “Gun use in the United States: results from two national surveys” (2000) – “How the Hemenway Surveys Distorted Estimates of Defensive Gun Use Frequency”


Utilizing trick questions and deceptive definitions, D. Hemenway gets his DGUs down and gun crimes up to support his claims.

Source : https://www.ssrn.com/abstract=3134859

Here are Gary Kleck’s responses :

1. Hemenway’s numbers are exceptionally low

Nearly all national surveys have yielded estimates of over a million DGUs per year, and the highest quality surveys have generated estimates over 2 million (Kleck and Gertz 1995; Cook and Ludwig 1996; Kleck 2001), 2 national surveys have yielded radically lower estimates – surveys done by David Hemenway and colleagues in 1996 (Hemenway and Azrael 2000) and 1999 (Hemenway, Azrael, and Miller 2000).

First, compare how low estimated DGUs are in both Hemenway’s work to other 19 national surveys.

Survey When Fielded %DGU Annual DGUs (in millions)
Cambridge Reports 1978 0.74 1.1
DMIa 1978 2.22 1.7
DMIb 1978 1.14 0.9
Hart 1981 2.01 1.7
Time/CNN 1989 4.5 2.6
Mauser 1990 1.5 1.4
Gallup 1991 1.93 3.6
Kleck and Gertz 1993 1.326 2.55
Gallup 1993 1.63 1.4
L.A.Times 1994 2.08 4
Tarrance 1994 0.51 1
NSPOF 1994 1.44 2.8
Hemenway and Azrael 1996 0.29 0.69
Hearst 1989 0.6 1.2
Hemenway, Azrael & Miller 1990 0.46 0.95
Gallup 1991 0.84 1.7
Washington Post 2000 0.96 2
CNN 2014 1.693 4.03
Pew Research Center 2017 1.037 2.6

(Numbers are adjusted for comparability. For example some surveys include uses against animals, include police and security guards uses, handguns only surveys, etc..)

The DGU annual estimate implied by Hemenway’s 1996 survey was the lowest ever obtained in a national survey in the list, while the 1999 survey yielded an estimate only slightly higher than the next-lowest estimates.

Thus, Hemenway’s DGU estimates are radically inconsistent with the results of 19 other national surveys conducted by a variety of organizations, including news outlets with strongly anti-gun editorial policies like the Los Angeles Times, Washington Post, and CNN, with estimates of annual DGUs in the U.S. ranging from 1 to 4 million.

2. But Hemenway’s numbers are higher than NCVS’s

It is worth noting that the Hemenway estimates are 7 to 10 times the “estimate” of DGUs supposedly implied by the National Crime Victimization Survey (NCVS), of roughly 65,000 (McDowall and Wiersema 1994) – the one that Hemenway has repeatedly endorsed (Hemenway 1997; Hemenway and Azrael 2000; Hemenway et al. 2000).

Even his own surveys’ results indicate that the NCVS-based “estimate” of DGUs is far too low.

3. Strategic wording to reduce DGU

Exact question in the 1996 survey : “In the past 5 years, have you used a gun in self-defense to protect yourself from a person or people?” [underlining in original]

Exact question in the 1999 survey : “In the past 5 years, have you used, displayed or brought out a gun in self-defense to protect yourself from a person or people?” [underlining in original]

Yourself and not others

First, the use of the phrase “to protect yourself” without the phrase “or others” has the

effect of arbitrarily excluding uses in which the gun was used to defend others.

Contrast this with the wording used in the Center for Disease Control and Prevention’s (CDC) Behavioral Risk Factor Surveillance System (BRFSS) surveys for 1996, 1997, and 1998: “During the last 12 months, have you confronted another person with a firearm, even if you did not fire it, to protect yourself, your property, or someone else?” (CDC 2018; emphasis added).

No firing, No DGU

Hemenway did not provide Rs with the instruction that they should report DGUs “even if you did not fire it.”

Gun with a bang flag
Ambiguity could be so useful in a survey.

Without this phrase, some people who had used a gun to threaten a criminal would think that their experience did not qualify because they did not fire the gun, assuming that the word “used” implied firing the gun. This could make a huge difference all by itself, since over 60% of DGUs do not involve the defender firing the gun.

4. Trap Question

1996 Version

In the 1996 survey, before asking the question intended to inquire whether the respondent (R) had committed a DGU, respondent was asked “In the past five years, has anyone displayed or brought out a gun in a hostile manner, even if this event did not take place during the commission of a crime?”

The question is extraordinarily ambiguous in at least three ways.

  1. The question could be interpreted as inquiring about either something the Respondent (R) did, or something that was done to the Respondent (R).
  1. The phrase “has anyone …” might also encompass things the R merely witnessed, or heard about second-hand. Indeed, of 122 Rs in the 1996 initially reporting a “hostile gun display,” 31 revealed that they were reporting something they had merely witnessed.
  1. What does the phrase “displayed or brought out a gun in a hostile manner” mean? It is possible to interpret this as crime victims defending themselves in a hostile manner against offender. Or vice versa, one could also interpret this as a hostile gun act that R witnessed.

Yet Hemenway and his team counted this as “criminal gun use”

1999 Version

Hemenway and his colleagues (2000) claimed to have reduced the ambiguity of this question in the 1999 survey, by making it clearer that they were asking about things done “against” the R, but this is not what their documentation for their 1999 survey indicates.

Question 22 reads “In the past five years, approximately how many times has anyone used, displayed or brought out a gun in a hostile manner?” The interviewer then told the R “I am going to ask you some question about the most recent time someone displayed or brought out a gun in a hostile manner” (ICPSR 2007).

Thus, the ambiguity of the 1996 question was not reduced in the 1999 survey.

In both surveys, the R could easily interpret the question as asking about either acts the R had committed with a gun or DGUs directed at the R, and, more specifically, could interpret the question as encompassing DGUs that Rs themselves had committed.

Additional Cunning in 1999 Version

Here is the significance of the authors asking this highly ambiguous question first, and then asking the question that was intended to inquire about DGUs.

Many of the Rs in this survey who had used a gun defensively would have answered “yes” to the first (“hostile display”) question with the DGU in mind.

Then when they were asked the question that was supposedly intended to measure DGUs, those who had interpreted the “hostile display” question as encompassing DGUs would have thought they had already reported the DGU in response to the earlier question.

Since it would not make sense for the surveyors to ask the same question twice, the most reasonable interpretation of the DGU question, for those that had committed a DGU, would be that it was asking about any additional DGU experiences the R might have experienced, beyond the one they thought they had already reported in response to the “hostile display” question.

Other than the few Rs who had multiple DGUs in the recall period, defensive gun users who interpreted the question this way would have to answer “No” to the DGU question, intending to indicate that they had experienced no additional DGUs beyond the one they believed they had already reported.

Hemenway et al., however, interpreted “no” responses to the second question to always indicate that the R did not have any DGU experiences.

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5. Long Recall Period in Both Surveys

For both surveys, the interviewers asked Rs to report DGUs that occurred in the 5 years preceding the interviews – a very long recall period.

Although some might think that victimization experiences are surely memorable enough for victims to recall all or nearly all of them even many years after the event, research by the Census Bureau during the development of the National Crime Victimization Surveys (NCVS) showed that this is clearly not so.

Most victimizations are minor, and a large share of them are not recalled in surveys.

For example, reverse record checks conducted during the development of the NCVS found that, even among crimes serious enough to have been reported to the police, most assaults were not reported to the Census Bureau victim survey interviewers (Dodge 1981; Murphy and Dodge 1981).

Use of a five-year recall period by Hemenway and his colleagues served to increase recall failure due to memory problems and to push the DGU estimates down.

Hemenway et al. never explained why they used so long a recall period, or acknowledged that it would tend to reduce estimates of DGU frequency.

6. Sample Bias – Under-representation of the Subpopulations Most Likely to Have a DGU

Both the 1996 and 1999 surveys were based on grossly biased samples of the U.S. adult population.

The bias was documented for the 1996 survey in Hemenway and Azrael (2000,p.260), but the article describing the 1999 survey did not report any evidence bearing on the issue of whether the sample was representative of the population, and said nothing in the text about the issue (Hemenway et al. 2000).

Both surveys severely underrepresented males. While the percent male should have been 49% if the sample were representative of the national adult population with respect to gender, the 1996 survey sample was only 42% male and the 1999 sample was just 41.5% male.

While 12% of the U.S. population is African American, only 8.5% of the 1996 sample and 9.0% of the 1999 sample were African-American

Worse still, there were way too few low-income people included in either sample. While 23% of the U.S. population in 1996 had a household income under $15,000, only 12.1% of the 1996 survey’s sample, and 9.3% of the 1999 sample had household incomes under $15,000 (Hemenway and Azrael 2000, p. 260; author’s analysis of ICPSR 2007).

The Hemenway samples systematically underrepresented the people most likely to suffer a direct-contact criminal victimization, and thus most likely to experience an occasion for using a gun for protection against crime – an obvious implication of the sample biases that Hemenway et al. did not share with their readers.

They could have partially compensated for these biases by using post-stratification weighting, but did not.

7. How David Hemenway spun his tales

In the 5 year period from 1995-1999, the NCVS estimated that there were 3,355,025 violent crime incidents in which offenders possessed, but did not necessarily use, firearms (U.S. Bureau of Justice Statistics 2000).

Pinocchio on red background
Hmm, he looks familiar. Is this guy a relative to someone I know?

Research by the Bureau of Justice Statistics (BJS) found that only 53.2% of the NCVS-reported events that are loosely labelled by BJS as “gun crimes” involve a gun actually being used to threaten or attack the victim.

If only 53.2% of the 3,355,025 were gun-linked violent crimes committed from 1995 through 1999, this means there were 1,784,873 such crimes – an average of 356,975 gun crimes per year.

Recall that the 1999 Hemenway survey, ignoring its critical flaws for the moment, indicated that there were 952,907 defensive uses of guns per year.

Thus, even this unusually low DGU estimate was 2.67 times as large as the NCVS-estimated number of gun crimes.

How then did Hemenway and his co-authors manage to claimed that “criminal gun use is far more common than self-defense gun use”?

Instead of using the results of the sophisticated NCVS regarding the number of gun crimes, they chose to compare the frequency of DGUs with the frequency of their ambiguous “hostile gun displays.”

They falsely claimed to know that these experiences were “criminal gun uses” (Hemenway et al. 2000, p. 266) even though that was not at all what the “hostile displays” question had actually asked about.

When Gary Kleck analyzed the raw data from their 1996 survey, he found that 75% of the Rs reporting a “hostile gun display” did not consider the display to be “part of the commission of a crime”.

8. Legal Opinions

Hemenway and his colleagues argue that it doesn’t really matter how many DGUs are reported in surveys because most of these uses were “probably illegal” and “against the interests of society” (Hemenway, et al. 2000, p. 263).

One of the more eccentric analyses performed by the authors involved asking 5 unnamed criminal courts judges for their opinions on the legality of 35 DGUs reported in the two surveys, based solely on summaries of the incidents crafted by the authors.

Sketchy Summaries

The authors provided only a very sketchy outline of their methods – a description that was more noteworthy for what it did not say than for what it did say.

The authors did not :

  • say why these particular 5 judges were picked (was there prior information that the judges had unusually narrow conceptions of lawful self-defense?).
  • 5 unknown people
    Who are these 5 judges?
  • Report any effort to match the state in which a reported DGU occurred with a judge from that state, nor would that have been possible given that the researchers only used judges from 3 states.
  • Provide readers with a copy of the instructions provided to judges describing their task.
  • Provide copies of the summaries of purported DGU incidents provided to the five judges.
  • Provide transcripts of Rs’ descriptions of their claimed DGUs (all easily posted in an online appendix).

Furthermore, the judges provided their opinions on just 35 claimed DGUs, far too few to yield meaningful estimates of the fraction of DGUs that are lawful.

It is worth pointing the out one-sided use that the authors’ made of these five judges. The judges were asked to assess the legal status of claimed DGUs, but not the experiences that the authors characterized as “hostile gun displays.”

This one-sided procedure had the effect of the judges effectively “disqualifying” some of the DGUs as lawful self-defense acts, while not “disqualifying” any of the “hostile gun displays” as “gun crimes.”

9. Decorative Caveats

Hemenway often engages in the practice of what could be called the “nonoperative Caveat.”

He draws a dubious conclusion from flawed research, then in the “limitations” section of his research report, weakly acknowledges a few of the flaws in his research (the caveats), but finally states conclusions that make sense only if one completely ignores the caveats.

Throwing garbage into the bin
Throw those caveats to trash and forget all about them. Huh? No, we don’t have any caveats.

The caveats seem to have been stated for the sake of superficially satisfying academic norms and pacifying journal reviewers, but have no influence on the conclusions that Hemenway and his coauthors draw.

The authors conceded that their sample of five judges was a convenience sample rather than a “random sample,” and also was “too small to be confident of the stability of the aggregate ratings we report here.”

This logically should mean that they could not generalize the judges’ rating to the full national population of reported DGUs.

Yet 2 sentences later the authors did precisely that: “Our results indicate that gun use against adults to threaten and intimidate is far more common than self-defense gun use by them, and that most self reported self defense (sic) gun uses are probably illegal” (p. 267).


Summary of the DGU Debate

DGU summary infographic

Want to use this image? Feel free to grab this code!



That sure was a long read.

Perhaps the only 2 things that can be learned from these research are that :

  1. Social science, unlike natural science, is quite elusive and hard to proof.
  2. People’s belief aren’t easy to change. Pro-guns will still be Pro-guns and Anti-guns will still be Anti-guns

Since nothing is conclusive about DGU at the moment, the probable advice is to go with anything that “floats your boat”.

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