A pair of mass shootings left a total of 31 people dead and many others injured over the course of just 24 hours this weekend.

22 people were killed at a shooting at a Walmart in El Paso, Texas on Saturday, while nine others were killed at another shooting in Dayton, Ohio early Sunday morning.

The incidents come just days after three other people were killed at a shooting at a garlic festival in Gilroy, Calif., and nearly two years after a gunman opened fire from the 32nd floor of a Las Vegas hotel, killing 58 people and wounding another 422.

A database of mass shootings compiled by Mother Jones going back to 1982 counts 114 such incidents in which at least three people were killed, not including the gunman. In that time, 932 people have been killed and 1,406 wounded, including the numbers from the El Paso and Dayton incidents. The following chart visualizes each mass shooting in terms of deaths and injuries. TIME has examined each incident and slightly adjusted some values as the death toll and number of injured has been clarified over time.

America’s mass shooting epidemic defies not only one’s sense of humanity, but also the basic practice of counting. There are several common means of tallying mass shootings with widely divergent results, based on, for example, whether one limits to incidents of indiscriminate killings versus targeted homicides. As Mother Jones‘ Mark Follman notes, the actual number of fatalities is probably higher. A 2013 federal mandate authorized by President Obama lowered the definition of a mass shooting down from four victims to three, which led to more of these shootings being tracked, but there may be earlier ones that are not included. The chart also does not include the thousands of killings each year in which there were fewer than three fatalities.

Correction, Aug. 7

Due to an editing error, the previous version of this story misstated in one instance the number of people who were wounded by gunfire in the Oct. 2017 Las Vegas shooting. It was 422, not 546.

Write to Chris Wilson at chris.wilson@time.com.