No matter how you define a mass shooting, one thing is clear: data suggests this brand of violence has grown worse in the United States.

In 2015 alone, there have been 299 shootings that killed or injured 1,487 people, according to Mass Shooting Tracker data, which counts at least four people wounded by gunfire as a mass shooting.

This year, 381 people died this way, according to the data. These shootings occurred at night clubs and children’s birthday parties, when long-time friends watched college football on TV and when churchgoers gathered for a weekly Bible study. These incidents have happened in 45 states and the District of Columbia, and happened at a rate of more than one shooting per day.

The largest recent mass shooting occurred one week ago and left 10 people dead, including gunman Chris Harper Mercer, at Umpqua Community College in Roseburg, Oregon, adding one more tally to a bleak list of places marked by gun violence.

Early Friday, law enforcement authorities said Steven Jones opened fire near a student dormitory at Northern Arizona University‘s Flagstaff campus, leaving one person dead and three injured.

There’s debate, however, about how to define a mass shooting.

In 2014, a Federal Bureau of Investigations report studied all mass shootings that involved an active shooter, or incidents where a person used firearms to kill or try to kill others “in a confined or populated area.”

Between 2000 and 2013, 486 people died in 160 active shooter incidents nationwide, the FBI report said. That’s about 11 such incidents per year, and the trend only increased over time. Overall, seven out of 10 incidents occurred a business, workplace or school.

And unlike Mass Shooting Tracker data, the FBI’s assessment included incidents where fewer than four people were shot, explained Adam Lankford, a criminal justice professor at the University of Alabama. However, the FBI data doesn’t include shootings of multiple people that occur in a home or other uncrowded setting.

These definitions shape the problem’s scale and pose a challenge in trying to better understand the factors that produce mass shootings, he said.

“However you talk about the problem, or type of shooter or shooting, that defines your results,” he said.

It’s too soon to know if 2015 will signal a turn in mass shootings, Lankford explained, but looking at more than a decade of data from the FBI, the outlook is grim.

“They found these incidents are clearly on the rise. That’s pretty strong evidence,” he said.

Editor’s Note: This post and its map has been updated to include the Oct. 9 shooting at Northern Arizona University campus that left one person dead and three more injured as well as other shootings to date, according to Mass Shooting Tracker data.