1. Mass shootings appear to have become more common, deadlier
Statistics about mass shootings in the United States can vary depending on the source because each uses its own criteria for what qualifies as a mass shooting.
Even so, all of them point to the same rising trend, both in terms of the number of attacks and the tally of victims.
One source of the data, investigative news outlet Mother Jones, has compiled 35 years’ worth of data about mass shootings. It defines a mass killing as the killing of at least four people in a public place in which the motive appeared to be indiscriminate killing.
Between 1982 and Nov. 7 of this year, there were at least 94 incidents that fit the Mother Jones definition of a mass shooting. Fifty, or more than half, of those incidents occurred in the past decade, including 10 already in 2017, which is more than in any previous year. And there are still nearly two full months left in 2017.
This year, as of Nov. 7, 112 people had been killed in mass shootings and another 520 injured, each of which are the highest totals in Mother Jones’ records.
In the wake of the latest mass shooting — Sunday’s massacre at a church in Sutherland Springs, Texas — three of the five deadliest mass shootings on US soil in modern history have occurred within the past 17 months.
Even more astounding, two of the five deadliest shootings (Las Vegas and Sutherland Springs) occurred within just 35 days of each other.
Sunday’s massacre in Texas also means that the 1999 school shooting at Columbine High School in Colorado, which once rocked the nation, is now tied with two other mass shootings as the 10th deadliest in the past 35 years.
2. In fact, by some measures, there have been more mass shootings than days in each of the past three years
The Mass Shooting Tracker is a project that tracks incidents in which four or more people are shot — but not necessarily killed — in a single spree or setting.
By its count, there were 371 such incidents in 2015, 477 in 2016, and 378 this year, as of Nov. 7. That meant there were more mass shootings than days in each year, an oft-cited statistic.
Where mass shootings occurred in 2016
This map is based on data from the Mass Shooting Tracker, which defines a mass shooting as a single incident in which four or more people are shot, regardless of whether they were killed. The definition allows for the shooter to count toward the four or more threshold. Others define mass shootings differenty. (Note: The size of each dot reflects the number of people who were shot.)
Matt Rocheleau/Globe Staff
3. Active shooter incidents are also on the rise
The FBI tracks statistics of “active shooter” incidents. An active shooter incident, to the FBI, involves one or more people “actively engaged in killing or attempting to kill people in a confined and populated area.”
The agency counted 220 such incidents between 2000 and 2016, and has noticed a rising trend.
4. The term ‘active shooter’ has rapidly become a part of our vocabulary
The Washington Post in late 2015 researched online search data from Google Trends to find how use of the two-word term has risen sharply in recent years.
5. Gun ownership in the US has declined overall
Gun ownership is at the lowest level in the United States since at least the early 1970s.
In 1973, 47 percent of American households reported having at least one gun. That figure peaked in 1977 at 50.4 percent, according to the most recent General Social Survey report by the University of Chicago. But since then it has trended downward.
In 2014, 31 percent of households in the US said they had a gun.
6. So, too, have gun homicide rates
The Pew Research Center reported that the gun homicide rate in the United States peaked in 1993 and has declined since, even amid the rise in mass shootings, which account for a relatively small number of gun homicides. As of 2014, the rate was 51 percent lower than the 1993 rate.
7. But both gun ownership rates AND gun death rates in the US are much higher than in any other highly developed country
The Small Arms Survey found that there were 88.8 civilian-owned guns per 100 people in the United States as of 2007. The next highest rate was 54.8 civilian-owned guns per 100 in Yemen.
And gun sales appear to have risen steadily in the United States in the years since then, with background checks for gun transactions — considered to be the best available indicator of gun sale trends — hitting an all-time high in 2016.
Gun ownership is also highly concentrated. A 2016 study by researchers at Harvard and Northeastern universities found that just 3 percent of adults in the United States own half of the country’s guns. It also found an estimated 7.7 million adults nationwide make up a group of so-called gun super-owners, stockpiling anywhere from eight firearms per person up to 140.
According to 2012 data from the United Nations compiled by the Guardian news outlet, the United States has the highest rate of firearm homicides among highly developed nations, 29.7 gun killings per 1 million people.
Active shooter incidents are also more common in the United States than in other countries, according to J. Pete Blair, a criminal justice researcher from Texas State University, who has closely researched such attacks.
Another stunning piece of data: Guns have killed more Americans in just the past half century than every war in US history, according to the news website Vox.
8. That fits with a pattern of there being more violence in US than in most other developed nations
A Duke University researcher found the rate of assault deaths in the United States to be higher than in other than in most other nations in the Organization for Economic Cooperation and Development.
9. Many gun experts believe strong gun laws reduce killings
Numerous studies have found that states with stricter gun laws tend to have fewer gun deaths.
The Harvard Injury Control Research Center polled dozens of leading gun experts, finding that a majority believe that having a gun in someone’s home can make it a more dangerous place.
The following chart shows how about 100 experts responded when the center posed this question to them:
10. Support for gun rights has increased, even in the wake of gun massacres
Polls by the Pew Research Center have found increasing support for protecting gun owners’ rights over the past 20 years, while support for measures to control gun ownership has trended downward over the same period.
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