On Gun Control (Part III): The Numbers Behind Self-Defense

One of the main arguments against gun control is that people use guns defensively to fight crime, so guns offer a net benefit to society. Reducing or banning guns will actually increase crime. Let’s investigate the numbers surrounding this argument.

Violent crime rates: The violent crime rate in 2011 was 386.3 (all crime rates in this article are per 100,000 inhabitants) [1]. Despite the low probability, it adds up over time. In 70 years, this translates to a 24% chance of being a victim of violent crime [2]! As a point of comparison, consider vehicular fatalities, which are a good measure of our baseline tolerance for risk. Deaths in car crashes occur at a rate of 10.6 [3], over 100 times lower, resulting in a chance of death of less than 1% over a 70 year span.

Regarding guns specifically, according to some slightly older numbers (1993-2001), about 11% of violent crimes involved guns [4]. Using the average crime rate of 386.3, this suggests that the rate of violent crime involving handguns is about 42.

Defensive gun use: There is vast disagreement on rates of defensive gun use. Estimates range from 100,000 to 2.5 million per year [5]. With 313 million inhabitants in the US, this results in rates somewhere between 31.9 and almost 800! The high value may be inflated due to a number of reasons, including the following:

  • Poor survey design. One of many problems is “telescoping,” i.e., counting older events as having occurred recently.
  • Perceptual biases. Just because you think your gun prevented a crime, doesn’t mean a serious crime was ever going to occur. “Whether one is a defender (of oneself or others) or a perpetrator … may depend on perspective. Some reports of defensive gun use may involve illegal carrying and possession … and some uses against supposed criminals may legally amount to aggravated assault… Protecting oneself against possible or perceived harm may be different from protecting oneself while being victimized.” [6]
  • Poor definition of what defensive use even means. “Imagine, for example, measuring defensive gun use for a person who routinely carries a handgun in a visible holster. How many times has this person ‘used a handgun, even it was not fired, for self-protection?’ … In this regard, much of the debate on the number of defensive gun uses may stem from an ill-defined question…” [7]

Because of these and similar arguments, I am throwing out the upper limit and replacing it by 300,000 defensive gun uses per year (a rate of 95.6). I’ll discuss the implications shortly.

Imagine if there were no more guns: So what if, magically, there were no more guns? Guns would no longer be used in crimes. Whether this would have any effect on the crime rate is unclear. Many perpetrators would probably just choose a different weapon. We can expect the crime rate to drop anywhere from zero to 42 with perhaps a most likely value of 10. The benefit of defensive gun use would disappear. The range of increase is between 31.9 and 95.6 with a most likely value in the middle. I converted these ranges to probability curves and computed the possible change in crime rate. The result is shown in the two figures below.

Individual probabilities for changes in crime rate

Individual probability curves for changes in crime rate

Calculated increase in crime rate

Probability curve for increase in crime rate

Based on this calculation, the most probable change is an increase in crime rate of about 50. Thus, we conclude that, even throwing out the suspect value of 2.5 million defensive gun uses per year, and given the existing gun culture in the United States, a complete gun ban would probably result in a modest increase in violent crime rates.

Of course, guns will not really disappear overnight – what we are facing today is stricter laws on purchasing guns.  If stricter gun controls make no change on defensive gun use, but do remove the guns from criminals, the increase in crime rate may be much smaller. Furthermore, if the value of 2.5 million counts incidents that are actually criminal, then we should expect a noticeable decrease in crime rates. If, however, the value of 2.5 million is credible and real, then it would constitute a very strong case for allowing, even encouraging, widespread weapon ownership (by “law-abiding citizens” of course).

The conclusion, then? Given the strong disagreements in the rates of defensive gun use, the possible implications of those disagreements, and the importance of defensive gun use to determining changes in crime rate, it is impossible to draw any satisfying conclusion. The various sides will, of course, cherry pick facts to make their case, but this kid ain’t gonna believe them. He’s just waiting for the experts to offer a believable value for defensive gun use.

If there is any conclusion to draw it’s that this matter isn’t in the end all that important. There is no way that there will be a complete gun ban in the US any time soon. The strictest outcome might involve universal and strict background checks at all gun outlets with prohibition on some types of weapons and ammunition. None of this can be expected to hinder “law-abiding citizens” from using handguns defensively nor will it decrease crime much. As far as an argument for or against current gun control legislation, self-defense doesn’t provide a strong case for either side.

Notes and References:

  1. http://www.fbi.gov/about-us/cjis/ucr/crime-in-the-u.s/2011/crime-in-the-u.s.-2011/violent-crime/violent-crime.
  2. This number is oversimplified. Crime rates are nowhere close to uniform; they vary across ages, sex, and socioeconomic status. Most victims of violent crime are minority men between 18 and 24 (http://bjs.ojp.usdoj.gov/content/pub/pdf/cv11.pdf). Based on age-specific rates, if you are 40 years old your chance of being the victim of a crime in the future is only 8%. If you have never been the victim of violent crime, you probably belong to a demographic that has an even lower crime rate than the average for your age. Nonetheless, the chance of being the victim of a violent crime is sizeable, given the seriousness of the consequences. Self-defense is not a consideration that we can just ignore.
  3. http://www-fars.nhtsa.dot.gov/Main/index.aspx.
  4. http://bjs.ojp.usdoj.gov/content/pub/pdf/wuvc01.pdf. Even though the figure is a bit outdated, it’s probably OK since the percentage has been fairly steady.
  5. National Research Council, Firearms and Violence, p 102, http://books.nap.edu/catalog.php?record_id=10881.
  6. ibid, p 106
  7. ibid, p 108
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5 Responses to On Gun Control (Part III): The Numbers Behind Self-Defense

  1. Duke says:

    I have some questions if you’d like to discuss the issues.
    1) You compare violent crime (not gun deaths) to car deaths. Crime includes many assaults not related to guns. Shouldn’t you compare gun death to car death? You’re comparing apples to oranges otherwise. If you look at death statistics, you’ll see in 2010 we had 12,000 homicide deaths in the US. According to official census data for 2009, the vehicle death date per 100,000 population is 11 (http://www.census.gov/compendia/statab/2012/tables/12s1103.pdf). In other words, the total number of vehicle deaths was 33,000 compared to 12,000 homicide deaths. Now, per your statement “11% of violent crime involve guns” that means only a portion of the 12,000 homicides are gun related, correct? Official numbers make the conclusion very clear. Vehicle deaths outnumber gun related homicides many times over. You imply it is the other way around but facts seem to say otherwise.

    2) You have given a limit of 300,000 gun related self defense cases per year. Since there are only 12,000 homicides per year, doesn’t that make the case for gun ownership? The number of successful self defense cases far outnumber the deaths. In other words, the good clearly outweighs the bad. Without guns to defend themselves, a portion of those 300,000 people would end up dead. Exact numbers aren’t needed to show rendering people defenseless will cause overall harm.

    3) All the data we have comes from police reports. It will be, by definition, heavily weighted towards crime and criminal action. The high death rate of 18-24 year old men is caused by drug gang related activity. You cannot form conclusions on legal self defense from numbers derived from illegal drug gangs, bank robbers, and thugs. Protecting yourself is not a crime (with a gun, ball bat, or whatever). It is unreasonable to expect police records to give you data on legal activity because they only compile illegal activity. That’s the problem with most gun arguments. They grab up gun statistics from police reports that have everything to do with criminal (and illegal) use of guns to commit crimes, but nothing to do with legal uses of guns to prevent crime. It is important we never confuse the two. They have nothing to do with each other.

    4) Overall violent crime has been declining for years. We are safer now than we’ve been in decades. I’ll never attribute that decline to gun ownership because the reasons are complex, but you can say honest people aren’t causing massive gun problems. In truth, there’s little real evidence legal gun ownership is an issue at all and certainly no reason for our government to elevate gun control into a jihad against the Second Amendment.

    These are just a few thoughts on your article. I hope you accept them as constructive because that is my intent. I have no aspirations of changing anyone’s mind but it never hurts to see alternate interpretations of an issue. I enjoyed reading yours and hope you continue to provide them.

    • You should totally aim to change people’s minds. My mind is always open to change, given the right arguments. In fact, the name of the series of articles changed from “An arguement for gun control” to “On gun control” primarily because I’ve yet to find a really convincing argument in favor of gun control. Here are my responses to your thoughtful comments:

      1a) I wouldn’t worry too much about the car death comparison. Ignore it completely if you want. I just meant to provide a point of comparison. The point is that there is enough violent crime that we can’t just ignore it. I suspect you agree with that.

      1b) As for the rest of the article, I think that discussing violent crime as a whole *is* the appropriate metric for comparison. Guns can be used defensively to prevent all sorts of badness, not just murder. For example, it’s considered OK to use a gun to prevent a rape or a robbery. The proper comparison is the one I made here: comparing how much badness guns cause (violent crime involving guns) to how much badness they prevent (violent crime prevented by guns).

      2) The question isn’t how many homicides overall, but how many homicides are caused by guns versus how many are prevented by guns. This comparison led to the conclusion that to the extent that the numbers on self-defense point to anything at all, they point to a positive outcome of gun ownership.

      3) I agree that we should be careful to use the correct data, but the self defense data don’t come from crime data. For example, the National Crime Victimization Survey (NCVS), is a survey of victims of crime.

      4a) I agree that crime has gone down. I agree that the reasons are complex. I agree that this probably means that legal gun ownership is not causing massive problems.

      4b) I strongly disagree with your characerization of a “government jihad against the Second Ammendment.” I argued previously that liberals must understand that just because somebody owns a gun doesn’t make that person a psycho. In the same way, gun advocates must understand that some people just don’t want guns around them. This doesn’t make them evil not does it make the gun control debate a government-sponsored conspiracy.

      • Duke says:

        Thank you for the thoughtful response. The only thing I might add concerns your item 4b). People suspect the government is not being totally honest about gun control for several reasons. For one, the steps Obama is proposing mirrors those used in Britain and Australia for gun confiscation. They are clearly using them as roadmaps. Both started by banning certain weapons and “universal registration” that was a thinly veiled gun owners database. From here, the list of banned weapons increased until they decided to use the database to go door to door and grab all the firearms. You can’t confiscate them until you know the owners. When we see the same approaches from our government, people become alarmed.

        Second, Obama, Bloomberg, and all the gun control organizations have clearly stated the end goal is to disarm the population. When those people start making laws on gun control, it’s not hard to see where it’s going.

        Many of the executive orders issued by Obama are clearly intended to punish legal gun owners. He’s asking doctors to snitch on their patients. He told the police to trace all guns used for crime to the original owners. They want a gun owners database. None of these things have legitimate law enforcement uses. We have a database of car owners but does it stop car accidents? If a maniac steals your gun, why would police trace it back to the original owner unless they wanted to involve that innocent person in a crime they didn’t commit?

        People look at the evidence and become suspicious of gun control laws. It’s a mistake to assume they are all wide-eye’d conspiracy loons. It would also help if Obama stopped using nutjobs like Bloomberg to push his agenda. Bloomberg would grab up BB guns while banning Big Gulps. Gun control needs reasonable people but he doesn’t have a single one. It makes people wary.

  2. Duke says:

    You might be interested in how police feel about gun control. Here is a large scale poll from a respected police web site:

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