Drivers of gun deaths in the United States

November 22, 2018

The United States is in the midst of a resurgence of the perennial debate over gun violence, gun ownership, and gun control. Advocates for gun rights have raised alarms about perceived threats to gun ownership. This movement is lead by the National Rifle Association (NRA), which has in the past few decades made resistancing gun control its central mission: decrying gun-control legislation as unconstitutional assaults on the Second Amendment. Fears of gun control legislation have repeatedly translated into increased gun sales, with an 'Obama Gun Boom' following Barack Obama taking office, which (by one estimate) translated into a $9 billion boost in gun sales.



By contrast, the growth in "mass shootings" has led to growing calls for gun control policies. According to one study, more people have been killed in mass school shootings in the past 18 years than in the entire 20th century. Since the shooting at Columbine High School in 1999, more than 219,000 students have experienced gun violence in their schools.



The United States is a global anomaly when it comes to guns. Despite amounting to less than 5% of the world's population, the U.S. owns nearly half of the 644 million civilian-owned firearms in the world. So we wondered: who is dying because of firerams in the United States? And what is the effect of so many guns on the public's health?

Who is dying from guns in the United States?

According to the U.S. Centers for Disease Control and Prevention (CDC), a total of 38,148 people died due to guns in 2016. This number includes people who were assaulted with a firearm, those who committed suicide using a gun, accidental gun deaths, and a small subset where no cause was specified on the death certificate (less than 1% of all gun deaths). The number of gun-related deaths has increased by 33.5% from 1999 to 2016.



A man in the United States is much more likely to die from a gun than a woman. When we look at gun deaths that are assaults and those that are suicides (together nearly 98% of all gun-related deaths), men were 5.8 times more likely to die by a gun than women.

Number of firearm deaths in the United States, 1999-2016

Source: U.S. Centers for Disease Control and Prevention. ICD-10 codes used are X93-X95 (assault by firearm) and X72-X74 (intentional self-harm with firearm).

Between 1999 and 2016, dying by a gun became more and more common. Gun assaults have risen by 36.5% among men but only 16.9% among women. The majority of gun-related deaths, however, for men and women alike was suicide by firearm (61.7% and 59.9%, respectively in 2016). Although men have seen an increase of 35.7% in their risk of suicide by gun, shockingly, women's rate have more than doubled (55.2%).

Where are people most likely to die from a gun?

The distribution of deaths due to firearm has considerable geographic variation. A person in Illinois is 1.9 times as likely to die from an assault using a gun than to commit suicide by gun. Similarly, the number of assaults are 1.7 times higher than the number of suicides in Maryland and New Jersey. High rates of violent assault in cities such as Chicago, Baltimore, and Camden are a likely driver of this finding.



However, in 42 states, the rate of suicides using firearms is higher than that from assaults. In some states, this ratio is strongly skewed. In seven states, a person is more than 5 times more likely to commit suicide using a gun than to be assaulted with a gun; in Idaho, the highest in the country, a person is more than 14 times more likely to commit suicide.

Gun deaths: assault or self harm? (2016)

Ratio of assault deaths to suicide deaths (by firearm) 0 - 0.15

0 - 0.15 0.16 - 0.30

0.16 - 0.30 0.31 - 0.45

0.31 - 0.45 0.46 - 0.60

0.46 - 0.60 0.61 - 0.75

0.61 - 0.75 0.76 - 0.90

0.76 - 0.90 0.91 - 1.05

0.91 - 1.05 1.06 - 1.20

1.06 - 1.20 1.21 - 1.35

1.21 - 1.35 1.36 - 1.50

1.36 - 1.50 1.51 +

Source: U.S. Centers for Disease Control and Prevention. Ratio is the age-adjusted death rate from assaults using firearms to age-adjusted death rate by intentional self-harm with firearm. ICD-10 codes used are X93-X95 (assault by firearm) and X72-X74 (intentional self-harm with firearm).

How is gun ownership related to gun-related deaths?

Understanding whether population- or individual-level gun ownership is associated with firearm death is complicated by a lack of national data. Federal law only requires the registration of firearms called 'Title II weapons,' a category that includes machine guns, short shotguns and rifles, and explosive devices such as rocket launchers and grenades. This regulation, codified in the National Firearms Act of 1934, means that the Bureau of Alcohol, Tobacco, Firearms and Explosives reports data on how many of these firearms are registered. By contrast, more common firearms such as pistols, revolvers, and shotguns are registered only where state law requires.



Since we don't know how well Type II weapons approximates total gun ownership, we used some estimates from a study published in the journal Injury Prevention, which reports representative survey data from the public opinion research firm YouGov on the percentage of respondants that own a firearm.



Are these numbers related to firearm-related deaths? We do see an increase in age-adjusted death rates due to firearm assaults or suicides. In fact, the relationship is approximately such that every 4% increase in the proportion of people that own a firearm is associated with a 1 per 100,000 increase in the age-adjusted death rate due to guns (R2 = 0.468). It doesn't explain all the variation in death rates, and there are some outliers (for example, Hawaii has above-average gun ownership yet very low gun-related death rates), but a correlation does exist.



Interestingly, we do not observe any relationship between the proportion of people owning guns and the rate of deaths due to assault with a firearm. This is in agreement with other articles on gun violence like this one on Medium. In fact, it is suicide by gun that seems to be the highest in states that have the highest gun ownership (R2 = 0.503). Of course, it's impossible to know whether the people that buy guns are predisposed toward making suicide attempts, whether gun ownership makes suicide attempts more likely to be fatal, or whether some other factor is driving this relationship.

Deaths due to firearms (2016) and percent of population that owns a gun (2013)

What about gun control policies?

The number of guns owned by a community are only one piece of the story. The number and types of laws that govern gun ownership can also impact gun-related violence and mortality. For example, policies that prohibit people with domestic violence convictions from owning a gun may prevent future assaults. Similarly, child access prevention laws could reduce the number of accidental deaths among children.



To describe this relationship, we extracted data on gun control laws from the State Firearm Laws database, a Robert Wood Johnson Foundation-funded initiative out of Boston University. The database tallies the number of laws in each state in a number of categories: dealer and buyer regulations, prohibitions for high-risk gun possession, background checks, ammunition regulations, concealed carry, domestic violence, 'stand your ground,' and more. Although simply adding up regulations is not an especially nuanced way of looking at gun control regulations, it does allow for relatively consistent comparisons across states.



We find that on average, states with more gun control laws have lower rates of assaults and suicides with firearms. This relationship is about a one-to-one correlation, with each new unique gun control law being correlated with a 1 per 100,000 reduction in firearm death rates. The relationship does not describe all the variation in the data (R2 = 0.259), but it is nonetheless fairly consistent.



Of note, the states that have a higher number of assaults than suicides (Illinois, Maryland, and New Jersey), all have a very large number of gun control policies. The states where most gun-related deaths are suicides, such as Montana, Wyoming, and Idaho, have few gun control laws.

Deaths due to firearms and gun control policies, 2016

Source: U.S. Centers for Disease Control and Prevention (age-adjusted death rate per 100,000) and the State Firearm Laws database (number of gun control policies). ICD-10 codes used are W32-34, X72-74, X93-95, and Y22-24. Coloring is matched to the map above.

How can we interpret these data?

According to a survey from Pew, protection is the most common reason identified for owning a firearm. However, the results from these data suggest that gun-related suicide may constitute a much greater threat for gun owners than does violent assault.



The relationship between gun ownership and suicide is not novel. In fact, scientists describe the percentage of suicides committed using a firearm as the best validated proxy for gun ownership (see for example the summary in this paper in the American Journal of Public Health); which is to say, it is well known that if you own a gun you are likely to use it in a suicide attempt.



Suicide, both with and without firearms, is a growing public health crisis, and one that is overwhelmingly impacting men. The elevated rates of firearm suicide rates in states with high gun ownership and fewer gun control policies highlight some potential avenues for addressing this issue.