A gunman killed 12 people and injured 15 others on Wednesday at a bar and grill in Thousand Oaks, California.

Nearly 13,000 people in the US were murdered with firearms in 2015 (the latest available data), not including suicides.

Gun violence is a leading cause of death in the US, according to the CDC.

In March, the US government moved to weaken a decades-old restriction on federal research into guns.

On Wednesday night at 11:20 p.m., a gunman that authorities have identified as Ian David Long entered the Borderline Bar & Grill in Thousand Oaks, California, and began shooting.

By early Thursday morning, the former US marine had killed 12 people, injured 15 others, and taken his own life.

The shooting is considered the 15th deadliest in recent US history, yet Long's victims join a growing number of people killed by guns in the US.

Wednesday's mass shooting follows the murder of 17 people at Stoneman Douglas High School in February and the killings of 11 people at the Tree of Life Synagogue in Pittsburgh in October.

This week's attack also happened a little more than a year after the deadliest in America: the Las Vegas Strip shooting, which left 58 people dead and 850 others injured. By chance, dozens of people who had survived the Las Vegas attack were also present for this week's shooting‚ and several of them were shot to death.

Read more: The NRA told doctors to 'stay in their lane' when it comes to gun deaths — and doctors are posting furious, devastating responses

Millions of people marched against gun violence this year, and Congress voted to loosen a restriction on the CDC's research of gun violence, which has been in effect for about 22 years.

Below is some of the most recent data available on gun violence in the US (highlighted in red; suicides and accidents excluded), and how it compares to other causes of death over the lifetime of an average American.

According to this analysis, assaults by firearm kill about 13,000 people in the US each year, and this translates to a roughly 1-in-315 lifetime chance of death from gun violence. The risk of dying in a mass shooting is about 35 times lower than that, with a 1-in-11,125 lifetime chance of death.

The chance of dying from gun violence overall is about 50% greater than the lifetime risk of dying while riding inside a car, truck, or van (a category that excludes pedestrian, cyclist, and other deaths outside of a motor vehicle). It's also more than 10 times as high as dying from any force of nature, such as a hurricane, tornado, earthquake, flood, or lightning strike.

These measures suggest Americans are more likely to die from gun violence than the combined risks of drowning, fire and smoke, stabbing, choking on food, airplane crashes, animal attacks, and natural disasters.

Where the data comes from

People comfort each other near the scene of the bar shooting in Thousand Oaks, California. Mark J. Terrill/AP

The chart above does not account for a person's specific behaviors, age, sex, location, or other factors that could shift the results; it's an average of the entire US population.

But it clearly shows that gun violence in the US is a leading cause of death, which is how the CDC describes firearm homicides in its National Vital Statistics Reports.

Most of the data comes from an October 2017 report by the National Safety Council and a November 2017 report by the National Center for Health Statistics on causes of death in the US, primarily those that occurred in 2015. (The NSC report uses 2014 data wherever newer data was unavailable.)

Mass shootings aren't part of the data sets above, but the Gun Violence Archive project keeps a sourced tally, which we've independently counted. The organization considers any event where four or more victims were injured (regardless of death) to be a mass shooting.

In 2015, some 333 mass shootings left 367 people dead, according to their tally. The statistics rose in 2016 to 383 mass shootings that killed 456 people. In 2017, there were 346 mass shootings that led to 437 deaths, and so far this year, we've seen 307 mass shootings.

Foreign-born terrorism data comes from a Cato Institute terrorism report, and some natural-disaster data comes from Tulane University.

We calculated the lifetime odds of death by applying 2015 life expectancy and population numbers in the US, and our analysis assumes each cause of death won't change drastically in the near future. (Mortality data from previous years suggests these rankings are relatively consistent, with the exception of skyrocketing accidental poisonings due to the opioid epidemic.)

You can view our full dataset and sourcing here.

A dearth of US gun-violence research

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Although gun violence is one of the leading causes of death in America, it is also one of the most poorly researched, according to a January 2017 study published in the Journal of the American Medical Association.

"In relation to mortality rates, gun violence research was the least-researched cause of death and the second-least-funded cause of death after falls," the study's authors wrote.

The study ascribed this dearth of research to restrictions — namely an addition to a 1996 congressional appropriations bill called the Dickey Amendment, which stipulated "none of the funds made available for injury prevention and control at the Centers for Disease Control and Prevention may be used to advocate or promote gun control."

This is the rule that Congress recently voted to weaken with its new funding bill, which Trump signed in March. The new provision gives the CDC explicit permission to research the causes of gun violence, though it maintains a ban on "using appropriated funding to advocate or promote gun control."

Research into gun violence is the most poorly funded relative to other causes of death. Dr. David E. Stark, Dr. Nigam H. Shah/JAMA

The previous lack of clarity on researching gun violence has hindered many scientists from better understanding the problem.

"The fundamental, foundational work of documenting the full scale of the health consequences of firearms has not been done," Sandro Galea, an epidemiologist and the dean of the Boston University School of Public Health, told Mother Jones in January 2017. "It's the kind of project that we do all the time. It just hasn't been done with firearms because there haven't been resources."

Although the Dickey amendment has been weakened, Republicans in Congress are reportedly uninterested in restoring $2.6 million in annual funding for CDC research into gun violence.

"[T]op GOP appropriators say they have no interest in funding new federal research into gun violence," The Hill wrote in April.

The research that has been conducted by private institutions like the Harvard Injury Control Research Center show a clear connection between gun ownership, gun availability, homicides, and violent death.

A roundup of gun-control and gun-violence studies by Vox shows that Americans represent less than 5% of the world population but possess nearly 50% of the world's civilian-owned guns. The data also reveals that police are about three times more likely to be killed in states with high gun ownership, countries with more guns see more gun deaths, and states with tighter gun control laws see fewer gun-related deaths.

This story has been revised and updated. It was originally published on February 15, 2018.