Get the Facts on Mass Shootings in the U.S.

Today's Events in Historical Context

A man prays before a memorial to the victims of the Pulse nightclub mass shooting in Orlando, Florida. Mass shootings in the U.S. have been on the rise for decades.
Matt Mitchell pays his respects at a memorial in front the Dr. Phillips Center for the Performing Arts to the victims of the Pulse gay nightclub shooting where Omar Mateen allegedly killed 49 people on June 14, 2016 in Orlando, Florida. The mass shooting killed at least 49 people and injuring 53 others in what is the deadliest mass shooting in the country's history. Joe Raedle/Getty Images

On June 12, 2016, The Pulse nightclub in Orlando, Florida became the site of the deadliest mass shooting in United States history. Shooter Omar Mateen, killed by police during a siege on the club, is alleged to have murdered 49 people and injured 53, bringing the total of victims to 102.

If it seems like the problem of mass shootings in the U.S. is getting worse, that's because it is. Let's take a look at the history of mass shootings to better understand current trends.

What Exactly Is a Mass Shooting?

To understand historical and contemporary trends in mass shootings, it's first necessary to define this type of crime. A mass shooting is defined by the FBI, first and foremost, as a public attack. It is categorized as distinct from gun crimes which happen within private homes, even when those crimes involve multiple victims, and from those that are drug- or gang-related.

Historically, a mass shooting has been considered a public shooting in which four or more people were shot. Up through 2012, this is how the crime was defined and counted. Since 2013, a new federal law reduced the figure to three or more, so today, a mass shooting is a public shooting in which three or more people are shot.

The Frequency of Mass Shootings Is on the Rise

Every time a mass shooting occurs there is a debate in the media about whether or not they are happening more often than they used to.

The debate is fueled by a misunderstanding of what mass shootings are. Some criminologists argue that they are not on the rise, but this is because they count them among all gun crime, which is relatively stable year-over-year. However, when we examine data on mass shootings as they are defined above by the FBI, we see clearly the disturbing truth: they are on the rise, and have increased sharply since 2011.

Analyzing data compiled by the Stanford Geospatial Center, sociologists Tristan Bridges and Tara Leigh Tober found that mass shootings have progressively become more common since the 1960s. Through the late 1980s there were no more than five mass shooting events per year. Through the 1990s and 2000s the rate fluctuated and occasionally climbed to as high as 10 per year. Since 2011, the rate has skyrocketed, climbing into the teens, and peaking at a horrifying 42 mass shootings in 2015.

Research conducted by experts at Harvard School of Public Health and Northeastern University corroborates these findings. The study by Amy P. Cohen, Deborah Azrael, and Matthew Miller found that the annual rate of mass shootings has tripled since 2011. Prior to that year, and since 1982, a mass shooting occurred on average every 172 days. However since September 2011, the days between mass shootings have decreased, which means that the pace at which mass shootings occur is accelerating. Since then, a mass shooting has occurred every 64 days.

The Numbers of Victims Is on the Rise Too

Data from the Stanford Geospatial Center, analyzed by Bridges and Tober, show that along with the frequency of mass shootings, the number of victims is also on the rise.

The figures for killed and injured have climbed from below twenty in the early 1980s, spiking sporadically through the 1990s to reach levels of 40 and 50-plus, to regular shootings with more than 40 victims through the late 2000s and 2010s. Since the late 2000s, as many as 80-plus to 100 victims have been both killed and injured in some individual mass shooting events.

Most Weapons Used Were Legally Obtained, Many Also Assault Weapons

Mother Jones reports that of those mass shootings committed since 1982, 75 percent of the weapons used were obtained legally. Among those used, assault weapons and semi-automatic handguns with high-capacity magazines were common. Half of the weapons used in these crimes were semi-automatic handguns, while the rest were rifles, revolvers, and shotguns. Data on weapons used, compiled by the FBI, show that if the failed Assault Weapons Ban of 2013 had been passed, the sale of 48 of these guns for civilian purposes would have been illegal.

A Uniquely American Problem

Another debate that crops up in the media in the aftermath of a mass shooting is whether the U.S. is exceptional for the frequency at which mass shootings occur within its borders. Those who claim that it is not often point to OECD data that measures mass shootings per capita based on a country's total population. When you look at the data this way, the U.S. ranks behind other nations including Finland, Norway, and Switzerland. However, this data is deeply misleading, because it is based on populations so small and events so infrequent so as to be statistically invalid.

Mathematician Charles Petzold explains in detail on his blog why this is so, from a statistical standpoint, and further explains how the data can be useful. Instead of comparing the U.S. to other OECD nations, which have much smaller populations than the U.S., and most of which have had just 1-3 mass shootings in recent history, you can compare the U.S. to all other OECD nations combined. Doing so equalizes the scale of population, and allows for a statistically valid comparison. When you do this, you find that the U.S. has a rate of mass shootings of 0.121 per million people, while all other OECD countries combined have a rate of just 0.025 per million people (and that's with a combined population three times that of the U.S.). This means that the rate of mass shootings per capita in the U.S. is nearly five times that in all other OECD nations. This disparity, however, is not surprising, given that Americans own nearly half of all civilian guns in the world.

Mass Shooters Are Nearly Always Men

Bridges and Tober found that of the 2016 mass shooting events that have occurred since 1966, nearly all were committed by men. In fact, just five of those incidents--2.3 percent--involved a lone woman shooter. That means that men were the perpetrators in nearly 98 percent of mass shootings. (Stay tuned for an upcoming post on why social scientists believe this is the case.)

A Troubling Connection Between Mass Shootings and Domestic Violence

Between 2009 and 2015, more than half (57 percent) of mass shootings overlapped with domestic violence, in that the victims included a spouse, former spouse, or other family member of the perpetrator, according to analysis of FBI data conducted by Everytown for Gun Safety.

Additionally, nearly 20 percent of attackers had been formerly charged with domestic violence. (Our upcoming post on the connections between men and mass shootings will delve into this as well. In the meantime, take a look at this post from the archives on masculinity and violence.)

An Assault Weapons Ban Would Reduce the Problem

Between 1994 and 2004 the Federal Assault Weapons Ban (AWB 1994) was in effect. It outlawed the manufacture for civilian use of some semi-automatic firearms and large capacity magazines. It was prompted into action after 34 children and a teacher were shot in a school yard in Stockton, California with a semi-automatic AK-47 rifle in 1989, and by the shooting of 14 people in 1993 in a San Francisco office building, in which the shooter used semi-automatic handguns equipped with a "hellfire trigger".

A study by The Brady Center to Prevent Gun Violence published in 2004 found that in the five years prior to the ban's implementation, assault weapons outlawed by it accounted for nearly 5 percent of gun crime. During its period of enactment that figure fell to 1.6 percent. Data compiled by Harvard School of Public health, and presented as a timeline of mass shootings, show that mass shootings have occurred with much greater frequency since the ban was lifted in 2004, and the victim count has risen steeply.

Keep in mind that semi-automatic and high-capacity weapons are the killing machines of choice for those who perpetrate mass shootings. As Mother Jones reports, "more than half of all mass shooters possessed high-capacity magazines, assault weapons, or both." According to these data, a third of the weapons used in mass shootings since 1982 would have been outlawed by the failed Assault Weapons Ban of 2013.