An analysis of every US mass shooting over the past 30 years shows that two small policy changes, restricting high-capacity magazines and introducing stringent background checks, might have saved over 500 injuries and deaths, reducing total casualties in mass shootings by 50%.
Various proposals have been set forth since 2012’s numerous mass shootings, ranging from much stricter gun regulations to arming more individuals in public spaces. Starting from Mother Jones’ list of US mass shootings over the past 30 years, I analyzed the potential impact of two proposals in particular: would a ban on high-capacity gun magazines have reduced casualties, and would stringent background checks of gun purchasers have reduced the number of shootings? I researched the incidents surrounding each shooting to determine whether each proposal would have had any impact. The data are summarized in the table below, with the full research spreadsheet available here.
| Shooting | Deaths | Injuries | Lives Saved | Injuries Prevented | Weapon Legally Acquired? | Notes |
| Totals: | 459 | 481 | 250 | 324 | Legal in 58 of 63 cases | 54% of deaths and 67% of injuries might have been prevented with the policies analyzed. |
| Newtown, CT Sandy Hook Elementary | 27 | 2 | 17 | 0 | Yes – legal weapons in same household | The shooter’s rampage was stopped by a quick police response. If the shooter had to reload 3 times as often, he would hit many less victims, as he fired on each victim multiple times. |
| Minneapolis, MN Sign Company | 6 | 2 | 1 | 0 | Yes | The shooter reloaded at least once during the shooting, and initially struggled with victims. |
| Oak Creek, WI Sikh Temple | 6 | 4 | 3 | 2 | Yes | In a public setting with many adults, it’s possible shooter would have been stopped while attempting to reload, or would have retreated outside more quickly if he had less capacity. |
| Aurora, CO Theater | 12 | 59 | 12 | 59 | Yes | A lucky form of weapon capacity control prevented a larger disaster, as the shooter’s weapon jammed and he was only able to fire roughly 1/3 of the 100 round magazine. A properly integrated background check system might have stopped the incident entirely. |
| Seattle, WA Cafe | 5 | 1 | 0 | 0 | Yes | It’s not clear that the gunman ever needed to reload, and though he had a history of mental health problems, he was never treated and never convicted of a felony. |
| Oakland, CA – Oikos University | 7 | 3 | 7 | 3 | Yes | HCM limit would have no impact here, but the shooter was expelled from school for behavioral issues, which might have been caught if this data were submitted to a comprehensive background check system. |
| Atlanta, GA – Health Spa | 4 | 0 | 4 | 0 | Yes | HCM limit and background check would have no impact here |
| Seal Beach, CA – Salon | 8 | 1 | 3 | 0 | Yes | The shooter reloaded during the shooting per police reports, so lowering weapon capacity would likely have lowered casualties. |
| Carson City, NV – IHOP | 4 | 7 | 2 | 3 | Yes | The shooter fired over 30 rounds per eyewitness accounts – lower capacity would have constrained him. |
| Tucson, AZ – Giffords shooting | 6 | 13 | 4 | 9 | Yes | Shooter was tackled and stopped while he tried to reload – direct evidence that lower capacity would have decreased the toll. |
| Manchester, CT – Beer Company | 8 | 2 | 4 | 1 | Yes | Shooter used two weapons and fired multiple rounds at many victims – had he been limited, he would have run out of ammunition earlier |
| Lakewood, WA – police officer shooting | 4 | 0 | 0 | 0 | No | Capacity limits might not have helped, as the shooter fired on four victims seated at one table, and hit all of them with his initial salvo. |
| Ford Hood, TX – army base | 13 | 29 | 9 | 19 | Yes | Shooter reloaded many times, and 30 round magazines enabled him to fire roughly 170 rounds before being shot himself by military police. Multiple soldiers attempted to charge the shooter – if he had only a 10 round magazine, it’s entirely possible that he would have been tackled and stopped upon initial reload. |
| Binghamton, NY – civic association | 13 | 4 | 9 | 3 | Yes | Shooter fired 99 rounds in total – this would likelybeen reduced if his weapon capacity were 1/3 as large |
| Carthage, NC – nursing home | 8 | 3 | 0 | 0 | Yes | Since shooter used multiple weapons and never reloaded, it’s unlikely capacity limits would have mattered. |
| Henderson, KY – Atlantis Plastics | 5 | 1 | 0 | 0 | Yes | Shooter did not use a high capacity weapon |
| Dekalb, IL – Northern Illinois University | 5 | 17 | 5 | 17 | Yes | This incident’s casualty count is quite low because the shooter first fired with a very low capacity weapon, his 6-round shotgun – enabling many students to escape the classroom. Shooter also had a long, documented mental health history. |
| Kirkwood, MO – City Council | 6 | 1 | 0 | 0 | Yes | Shooter used low-capacity revolver initially, and took a higher capacity weapon from a victim (police officer). |
| Omaha, NE – Westroads Mall | 8 | 4 | 5 | 3 | No | Shooter appears to have emptied one magazine and then taken his own life. |
| Crandon, WI – sheriff’s rampage | 6 | 1 | 0 | 0 | Yes | Shooter used a service weapon, so proposed rules/limitations would have had no effect. |
| Blacksburg, VA – Va. Tech | 32 | 23 | 32 | 23 | Yes | Shooter reloaded many times, and used multiple weapons. Mental health check would have prevented weapons acquisition. |
| Salt Lake City, UT – Trolley Square | 5 | 4 | 5 | 4 | Yes | Shooter did not use high capacity weapons |
| Nickel Mines, PA – Amish School | 5 | 5 | 2 | 2 | Yes | Once shooter started firing, sheriffs approached – he killed himself as they arrived, and likely would not have had a chance to reload. |
| Seattle, WA – Capitol Hill | 6 | 2 | 6 | 2 | Yes | Shooter had a weapons-related felony charge, which was reduced to a misdemeanor. |
| Goleta, CA – postal shooting | 6 | 0 | 6 | 0 | Yes | Shooter had a previous history of mental illness |
| Red Lake, MN – high school | 9 | 5 | 3 | 2 | Yes | Shooter possessed a gun in his bedroom despite being treated with Prozac. Since he was an adolescent, and his parents/guardians chose to give him a gun, background checks would be ineffective. Shooter shot his grandfather who was a police officer, and took his weapons. |
| Brookfield, WI – Church group | 7 | 4 | 2 | 1 | Yes | Shooter suffered depression, but had no mental health or criminal records. |
| Columbus, OH – concert | 4 | 7 | 0 | 0 | Yes | No HCM used, and no medical or criminal record. Nearby police stormed the concert and shot suspect |
| Meridian, MS – Lockheed Martin | 8 | 7 | 4 | 3 | Yes | Shooter used military-style weapon with high-capacity |
| Melrose Park, IL – Navistar | 4 | 4 | 4 | 4 | Yes | Shooter used military-style weapon with high-capacity, and was also a convicted felon |
| Wakefield, MA | 7 | 0 | 5 | 0 | Yes | Shooter used high-capacity weapon and also had a history of mental illness, but with the mental illness far in his past and no criminal record, even stringent checks might not have denied him weapons. Shooter stopped firing at an arbitrary point and sat calmly til arrested. If he had lower capacity weapons, stopping to reload multiple times might have caused him to sit and wait for arrest earlier. |
| Tampa, FL – hotel | 5 | 3 | 5 | 3 | Yes | Shooter was arrested for assault only a few months earlier, and bought weapon at a gun dealer |
| Honululu, HI – Xerox | 7 | 0 | 3 | 0 | Yes | Shooter acquired a large number of weapons long before mental issues began. |
| Fort Worth, TX – Wedgwood Baptist Church | 7 | 7 | 2 | 2 | Yes | Shooter committed suicide after emptying three magazines – but he had six more loaded. Has the magazines been 1/3 smaller, that would have lowered the toll proportionally. |
| Atlanta, GA – Day trading | 9 | 13 | 0 | 0 | Yes | The shootings happened in multiple separate incidents, making it less likely that HCM limits would have had an impact. Barton was suspected but never charged in earlier murders, so background checks would have had no impact. |
| Littleton, CO – Columbine High | 13 | 21 | 6 | 10 | No | Shooters used a high capacity Tec-9 and standard capacity 9mm, so avg capacity is used here. Details of the shooting indicate that in many cases shooters fired at the same victim multiple times – if limited in capacity, this would have reduced their ability to fire on additional victims. |
| Springfield, OR – Thurston High | 2 | 24 | 1 | 19 | Yes | Shooter was tackled and stopped when he first tried to reload – a clear indication that lower capacity would have further limited casualties. |
| Jonesboro, AR – Westside Middle School | 5 | 10 | 2 | 3 | Yes | Shooters ran away after firing 30 rounds – lower capacity might have reduced total rounds fired. |
| Newington, CT – Lottery worker | 4 | 0 | 0 | 0 | Yes | Shooter chose specific victims and fired relatively few rounds, so capacity limits make no difference here. |
| Orange, CA – Caltrans | 4 | 2 | 3 | 1 | Yes | Shooter entered shootout with police shortly after initial incident, lower capacity might have shortened his attack |
| Aiken, SC – RE Phelon Co | 4 | 3 | 0 | 0 | No | Standard capacity weapon (illegally acquired) used |
| Fort Lauderdale, FL – city employee | 5 | 1 | 0 | 0 | Yes | Standard capacity weapon used |
| Corpus Christi, TX – Walter Rossler Co | 5 | 0 | 0 | 0 | Yes | Standard capacity weapon used |
| Fairchild AFB, WA – hospital | 5 | 22 | 5 | 22 | Yes | Shooter possessed only one 75 round drum magazine – so he would never have to reload. Military police arrived quickly and killed perpetrator. |
| Aurora, CO – Chuck E Cheese | 5 | 0 | 0 | 0 | No | Shooter fired less than 10 times, executing each victim, usually with a single shot |
| Garden City, NY – LIRR | 6 | 19 | 2 | 6 | Yes | Shooter emptied two 15 round magazines and was tackled while reloading with a third magazine. Total rounds fired would have been decreased by 1/3 were magazine capacity limits in place. |
| Fayetteville, NC – Luigi’s Restaurant | 4 | 6 | 2 | 3 | Yes | Shooter used a high capacity rifle, shooting was stopped by nearby police |
| San Francisco, CA – 101 California St office building | 8 | 6 | 4 | 3 | Yes | Shooter used a 32 round Tec-9 in the shooting, and fired hundreds of rounds |
| Watkins Glen, NY – office | 4 | 0 | 0 | 0 | Yes | Shooter killed four intentional targets with relatively few shots, and then waited for police to arrive – perhaps less than 10 shots total fired. |
| Olivehurst, CA – Lindhurst High School | 4 | 10 | 0 | 0 | Yes | Shooter used two weapons and fired relatively few shots, so high capacity weapon limits would have no effect here. Shooter also had no prior criminal or mental history. |
| Royal Oak, MI – postal | 4 | 6 | 4 | 6 | Yes | Shooter had his concealed weapons permit revoked on concern of mental illness. Shooter also used high-capacity magazines with his rifle and fired scores of rounds according to police. |
| Iowa City, IA – Univ of Iowa | 5 | 1 | 0 | 0 | Yes | Did not use a high-capacity weapon, and did not display sufficient signs of mental illness prior to shooting to warrant attention |
| Killeen, TX – Luby’s Cafeteria | 20 | 24 | 8 | 10 | Yes | Used high capacity pistols and reloaded multiple times – capacity limits would have enabled more victims to escape, as many escaped by exiting the restaurant. |
| Jacksonville, FL – GMAC plant | 9 | 4 | 9 | 4 | Yes | Shooter had a history of violence and convictions, and yet legally purchased multiple weapons. Used a high capacity weapon in shooting |
| Louisville, KY – Standard Gravure Co | 8 | 12 | 8 | 12 | Yes | Shooter used high capacity weapon, emptying its magazine and committing suicide with his second weapon. Shooter also had a lengthy psychiatric history including hospitalization |
| Stockton, CA – schoolyard | 5 | 29 | 5 | 29 | Yes | Shooter had a lengthy arrest history and had served time in jail as an accomplice to armed robbery, and yet was allowed to buy weapons. |
| Sunnyvale, CA – ESL Co shooting | 7 | 4 | 7 | 4 | Yes | Shooter was able to purchase guns while under a court restraining order |
| Palm Bay, FL – shopping center | 6 | 14 | 6 | 14 | Yes | Shooter used a high capacity .223 caliber rifle, and killed two police officers during the shooting – one of them as the officer was trying to reload. Perhaps if the shooter’s capacity were lower, the officer might have himself fared better. Gunman also had prior assault conviction. |
| Edmond, OK – USPS | 14 | 6 | 0 | 0 | Yes | Shooter was in National Guard and would have had access to weapons. Though he was referred to as “Crazy Pat”, he had no history of crime or treated mental illness |
| San Ysidro, CA – McDonalds | 21 | 19 | 14 | 13 | Yes | Shooter used a high capacity weapon, Uzi, pinning down a quick-responding officer with 30 rounds of fire before re-entering restaurant |
| Dallas, TX – nightclub | 6 | 1 | 0 | 0 | Yes | Shooter used an unknown handgun, emptying it into crowd and then rushing out – unclear that capacity limit would have any impact here. |
| Miami, FL – welding shop | 8 | 3 | 8 | 3 | Yes | Shooter did not use a high capacity weapon, but purchased his weapons one day after failing a psychiatric exam ordered by his employer, the school district, and after incidents in which he appeared to be a threat to students |
| Birchwood, WI – hunting altercation | 6 | 2 | 3 | 1 | Yes | Shooter fired 20 rounds at other hunters – if he had a lower capacity, it’s likely that another hunter would have been able to respond with fire |
The analysis above attempts to answer the question – what would have happened in these incidents had the proposed laws been in place? Of 459 deaths and 481 injuries in 63 shootings, I estimate that 250 deaths and 324 injuries (54% of deaths and 67% of injuries) might have been prevented with the analyzed proposals. Each proposal, its method of action, and the analysis approach is described further below.
High-Capacity Magazine Ban:
Definition: Sales of high-capacity magazines to and between private citizens would be completely banned, and imports of high-capacity magazines for private use would be banned as well. While many magazines would exist in private hands, a magazine buyback could then be used effectively, as magazines are relatively inexpensive.
Method of Action:
- In some instances, the shooter was disarmed by potential victims while trying to reload – smaller magazine size clearly would have limited total impact in these shootings.
- In some instances, potential victims fled during breaks in the shooting enabled by reloading – if a shooter has to reload 2 or 3 times as often, this effect is multiplied.
- In some instances, law enforcement arrived relatively quickly, and most damage in the shooting was done via the initial magazine – a smaller magazine would have limited impact in the shooting in these instances.
- In a few instances, victims attempted to rush the shooter immediately. If a shooter could only fire 10 shots instead of 20-50, it’s possible that he might be tackled quickly rather than be able to continue shooting.
- In most instances, the shooter committed suicide after doing a certain amount of shooting, but always before exhausting ammunition. Since each reloading represents a break in the act, some shooters would commit suicide after having fired fewer total rounds if they were capacity constrained.
- In a few instances, the shooter appeared to choose a specific weapon because of its high capacity. If high capacity magazines were not available, would the shooter still go forward with the attack?
- In 18 of 63 shootings, shooters fired relatively few rounds, chose a small number of specific victims, or used standard capacity weapons. In these instances the high-capacity magazine ban has no impact. 29% of actual mass shootings fell into this category.
Analysis Method: If the shooting fell into the last category above, then zero impact is noted in the analysis. Otherwise, the casualty count is reduced by the ratio of the shooter’s magazine size to standard magazine size – if the shooter used a 30 round magazine, then the casualty count is estimated at 2/3ds lower (rounded up) with a standard capacity magazine. This approach will tend to underestimate the effect of a ban in instances like 1,4, and 6 above, while providing an accurate estimate or an overestimate in instances like 2, 3, and 5 above. In aggregate, I think this approach is unbiased.
Stringent Background Checks:
Definition: Create a mandatory national database of all felons, mentally ill, and others posing threats (anti-terror lists, those who have made threats against schools or other institutions). Mandate that all firearms transactions for new and used weapons, in public and private transactions, be checked against this database, with instant results. This stands in contrast to the current background check system, which is done on paper and via telephone call, not electronically.
Method of Action:
- Out of 63 mass shootings over the past 30 years, only 5 have involved illegally purchased weapons. Some of the shooters had a history of mental illness or a criminal record – preventing a sale of firearms to these individuals would reduce the frequency of shootings.
- Many of the shooters with a history of mental illness had no criminal record – it’s unlikely that they would know how to obtain an illegal firearm.
- Some of the shooters purchased weapons in the days after making threats against a school or other institution – in these cases, a properly implemented stringent background check system would have prevented the weapon sales.
Analysis Method: Shootings were identified in which a shooter had a documented history of mental illness, a criminal record, or had made threats against an institution prior to buying a weapon. In these cases (17 instances total) it’s assumed that the casualty count is reduced to 0, as the shooter would have been unable to obtain a weapon. In reality a certain number of shooters would then try to acquire weapons illegally, and some might succeed. But a certain number of mentally-ill or former felons might never try to obtain a weapon if they knew they had no easy or legal means to do so, providing an offset.
Analysis of Assault Weapons Ban and Armed Civilian Presence
Two other proposals have been mentioned in the last several months – a ban on assault weapons and the placement of more armed guards or civilians in public places. On the question of assault weapons, the data from mass shootings shows that shooters preferred a range of semi-automatic weapons with high-capacity magazines. Weapon capacity makes a difference, but the type of weapon (handgun vs rifle) does not.
With regard to armed bystanders, in 9 of 63 shootings armed individuals (often police officers) were present. In several cases armed individuals became victims in the shooting, and the presence of armed individuals did not prevent the shooting from taking place. However, this analysis is by definition incomplete – this is an analysis of shootings that actually did take place, and doesn’t include data on shootings that were stopped by armed individuals. The evidence here suggests that the element of surprise may render concealed weapons somewhat ineffective, but this is not a conclusive finding.
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there are so many assault weapons and high capacity magazines that have been sold because of the scares of bans that there will never get total control of any of it now.. so by this being said , just arm everyone and after 5 or 10 years. make a chart on facts that it works or doesn’t … than work on some type of control …
this report is so subjective and completely without any real basis. The analysis is someone’s opinion – there is no scientific approach here and quite frankly I believe that the article is completely worng.
The issue is serious since some people live in fear just to send their children to school or go to a movie. I do not believe that an integrated system of background checks would prevent many of the mass shootings, nor do I believe that assault weapons bans will do much good. They do not go far enough. People who say that if we ban or limit certain types of gun sales only criminals will get access to them. The truth is that most of those who commit mass murders or even single shootings are not known and convicted felons or mental patients. The most dangerous armed person is probably someone you know who gains easy access to a gun and uses it due to a mental breakdown, or a moment of passion. We should pass laws prohibiting sales of all high capacity magazines and certain types of bullets, requiring background checks that take an entire month to clear, and enforcing more rigorously gun seller regulations. I am all in favor of comprehensive gun safety laws, none of which violate the Second Amendment. You can have your rifles for sport and hunting, but other types of guns should be strictly regulated. Thanks for this analysis.
Yeah – this is very much a complete joke. More people are still murdered every year by hammers, knives, medical malpractice, drunk driving and texting while driving. Find a REAL cause to take up.
What cause have you taken up? The cause of detracting those who are interested in reducing the deaths and injuries involved in firearm violence?
Thank you for the work on this subject, it was very informal and unlike most “research” into the subject.
State Crime Rates show scant linkage to Gun laws. http://www.washingtontimes.com/news/2013/jan/24/states-crime-rates-show-scant-linkage-to-gun-laws/#.UQLRbQISB5M.facebook
Why do you need assault rifles‘ or high capacity‘magazines?
By Rob Olive
Article says “In 1960, President John F. Kennedy reminded us:
―
Although it is extremely unlikely that the fears of governmental tyranny which gave rise to the Second Amendment will ever be major danger to our nation, the Amendment still remains an important declaration of our basic civilian-military relationships, in which every citizen must be ready to participate in the defense of his country. For that reason I believe the Second Amendment will always be important. “
You completely fail to take into account the practice of “Tactical Reloading”. Search it on YouTube and watch Tactical Reloading of semi-auto handguns, shotguns, ar-15s and even a revolver. Take a look at tactical reloading of a revolver by Massad Ayoob at https://www.youtube.com/watch?v=oXUwI_d8JlA Takes him about 2 secs to reload a revolver. Another video shows a shotgun reloaded with 8 shells in 5 secs. You are naive to think that limiting capacity will limit deaths by deranged lunatics. Disarming, and disabling the law-abiding from defending themselves against the criminal element and lunatics is not the solution. The police are always saying they need more capacity to keep up with the criminals. The criminals will always get what they need illegally, as they will come in with their drugs. Just remember that 75% of the caulk lines on the ground have criminality in their background and DO NOT represent the community at large. Funny the last five mass shooting where done by Liberals or children of Liberals. Maybe if we deny Liberals access to guns, we would all be a whole lot safer. All mass shooting in the last 50 years, except the Giffords shooting was done in “Gun-Free” zones. Why do you think the Lunatics pick Gun-Free zones?
Wayne, consider reading the detailed histories (in links above and in the spreadsheet) and observe the following:
1. In some instances, shooters committed suicide after a reloading pause – this has nothing to do with the speed of reloading, but with the fact that reloading provides a contemplative opportunity.
2. In other instances, shooters were tackled or fired upon by armed civilians or police officers when they attempted to reload. Consider that even in your preferred situation, where armed civilians are present – they rarely have an opportunity to draw and fire until initial fire has temporarily paused, during reloading.
3. There is considerable documentary evidence that in many shootings, potential victims were able to flee during brief pauses caused by reloading, weapon jams, and the like – this is precisely what capacity limits would make more common.
4. Finally, consider common sense – why do you personally want no limits? You would prefer, I assume to be able to fire more rounds consecutively rather than less. If tactical reloading really enables you to fire in an unimpeded manner, then you should have no issue with magazine/clip capacity limits. Consider also that in all of the high casualty mass shootings, larger magazines were utilized. At the logical extreme, a man with a single-shot bolt-action rifle reloading after every shot does far less damage than the same man with a semi-automatic weapon and a large magazine. This is common sense.
If after reading the historical record, you still come to the same conclusions, then I suspect that you have not tried very hard to use reason and fact in building your argument.
I don’t think there’s serious doubt that lower capacity magazines and background checks would save lives in mass shootings. The question is how many lives would be saved, which is exactly where your analysis falls flat on its face.
“The casualty count is reduced by the ratio of the shooter’s magazine size to standard magazine size.” This is called “pulling numbers from where the sun don’t shine.” The time it takes to change magazines is minimal, which reduces the difference between high capacity and proposed standards. That’s why guns use magazines to begin with, right? If you assume 1 shot per second and 5 generous seconds to reload, it takes 65 seconds to fire 60 shots from 30-round magazines, but a 10-round magazine would fire 45 shots in that time. That’s a 1/3 reduction, not 2/3. In some cases you might argue a larger reduction because of the other effects. That’s fine, but there’s no way it’s nearly as large as you’ve assumed.
Also, whenever there’s a chance a background check would have prevented a shooting, you’ve assumed that it would have. Take the recent Aurora, CO shooting. This guy clearly thought through and prepared — being rejected from purchasing a weapon might not have prevented him from acting. Maybe he would have found another way to get his guns. Maybe he would have turned to another weapon (a bomb or somesuch). Or maybe a proper system would have alerted the authorities that there was a dangerous person seeking to hurt people, and everything would have been different. We’ll never know.
The point is, what percentage of these shootings would have been prevented? Not 100%, surely, not with the proposed legislation. Unfortunately, nobody knows what the percentage should be, so we have to start making up numbers at some point. But I’ll let you pick a number more reasonable and see where your numbers land.
Doug, I guess you still haven’t read or comprehended the Method of Action section for the high capacity magazine limit. The “other” effects as you put it, are quite large, as indicated by the data in the 63 shootings – and these are what make the ratio used a reasonable estimation.
With regard to background checks – I note in the Method of Action section there that they would not actually work 100% of the time – some might go around them by various means. But others might be deterred from even bothering, so it’s not clear how much total efficacy would be reduced, if at all. The evidence from weapons laws in Australia and Israel has been quite positive – apparently laws can and do work (Australia’s incredible drop to 0 mass shootings in more than a decade, and Israel’s 60% reduction in soldier suicides).
I have read and understand, thank you.
Let’s look at my previous example. Using the 30-round clip, 60 rounds are fired with one reload. Using a 10-round clip, 45 rounds are fired with four reloads.
So, that equates to four times as many opportunities for someone to charge. Four times as many opportunities to run away. Four times as many opportunities for someone to commit suicide.
Point in your favor.
But life just isn’t that simple, and you know it. Look at how many examples in those 63 shootings where the shooter reloaded multiple times, without anybody charging. Yes, there are more opportunities, but you’re arguing that people will act 3 times faster if the clip is 1/3 the size. Surely you see the absurdity in that thinking. The same goes for committing suicide. Yes, there’s more opportunities for the shooter to contemplate the next step, but to say that’s going to happen 3x sooner.
The effects here are clearly nonlinear, and you have made zero attempt at quantifying this. Instead you assume that the effects of reducing.
Background checks. Yes, you acknowledge that 100% is not realistic … but when actually calculating the number of lives saved, in any case where a background check might worked you count for 100% lives saved and injuries prevented anyway. You justify this with a qualification: “But a certain number of mentally-ill or former felons might never try to obtain a weapon if they knew they had no easy or legal means to do so, providing an offset.” This goes outside the bounds of your study: “Starting from Mother Jones’ list of US mass shootings over the past 30 years, I analyzed the potential impact of two proposals in particular: would a ban on high-capacity gun magazines have reduced casualties, and would stringent background checks of gun purchasers have reduced the number of shootings?” Not trying to get a weapon and being denied a weapon are effectively the same thing for the purposes of your study.
The fact of the matter is that the numbers you found represent an upper bound — the most number of lives that could have been saved in these shootings given ideal conditions. If you count in human nature and other realities, I would expect the number to drop dramatically.
I’ll repeat one thing for clarity: I absolutely believe that background checks and limits on magazine sizes are effective. I just think you’re inflating the numbers significantly.
Also, a couple quick questions.
Under the Method of Action for the high capacity magazine ban, what’s the difference between 1 and 4? Which examples illustrate these differences?
Method of Action for background checks: can you give a citation for #2? I think it’s an interesting theory, but not one that fits the available data.
Doug,
You are right that the effects are non-linear, and they might best be modeled as a Markov chain of stateful probabilistic events. The effects of this actually cut both ways, as demonstrated by this example: consider the Ft. Hood shooting, in which several (unarmed) soldiers rushed the shooter. Had he been limited in capacity, he might well have been tackled and stopped after emptying one 10 round magazine. In that case, he would have fired a total of 10 rounds, not 170 as happened in reality. This is a reduction of 94%, not a reduction of 2/3 as modeled. There are numerous other cases (Tucson, Jonesboro AR, Fairchild AFB, Springfield, OR, etc) where a shooting stopped after exactly one magazine was emptied – in this case my model is accurate as well. When it comes to the 0s (cases where the limit has no impact at all based on the case history), I have excluded these – so it’s not as though I applied a blanket ratio across the board. As I said in the original methods of action, in some cases the model will overestimate the impact of the ban, and in some cases the model will underestimate it, but on net I believe it to be unbiased. And while it might be interesting to build a more realistic Markov-style model, I simply don’t have the additional data needed to do it (how centrally distributed are the first shots fired versus later shots, what is % chance of suicide at reloading, what % of people try to flee during breaks, etc).
I was going to let your last, insightful comment be. Ultimately, we don’t have nearly enough data to paint a complete picture. But, speaking about data, recent details from the Newtown shooting are instructive.
To summarize, the shooter took ten 30-round magazines. In the end, three were completely empty, three went unused, three were 1/3 to 1/2 full, and the one still in the gun was half-full. In total, as many as 162 shots were fired from this weapon (assuming all magazines were fully loaded to start, with one in the chamber). 154 casings were found, so the numbers add up decently well (Will 8 more show up at some point? Scary thought.)
To achieve the same number of shots, a 10-round limit would have required 16 magazines at least, possibly more. (Did the half-used magazines jam or did the shooter use tactical reloading? Would the shooter have emptied the 10-round magazines or reloaded sooner? We may never know.)
Anyway, I think we can safely assume that needing 16+ magazines instead of 10 (of which only 7 were used) might have limited the number of shots, and possibly saved lives, if it’s hard enough to carry around and use. On the other hand, maybe the shooter would have been more conservative with ammo which would have been a bad thing (162 shots in 300 seconds with “only” 29 victims makes this something to consider).
Given the details recently released, I want to look at your methods of action:
1) Doesn’t apply. The shooter chose a school, where there are few people to disarm him, not a military base.
2) Might apply. Especially if a 10-round limit leads to using a backpack to haul around the magazines, increasing the amount of time to reload, but that’s starting to speculate.
3) Obviously doesn’t apply — everything was over before law enforcement arrived, and the shooter was on his 7th magazine by that point.
4) Doesn’t seem to apply. See #1 above.
5) At first, I thought this applied pretty well. The problem is that the shooter didn’t stop at a reloading opportunity (there were still 15 rounds to be fired!). Fact is, we don’t know why he stopped — my best guess is a lack of convenient targets, leaving only himself.
6) Who knows on this one. The shooter was pretty determined in this case (planning and studying for a long time), so I’m currently thinking that this doesn’t apply.
7) Obviously doesn’t apply.
So, yeah. I hate to sound cold here. Magazine limits would have helped, but only maybe. As long as he had ammo and targets …
So anyway, I’m going to leave things at that, some points to consider.