If you look at mass shootings over time, two things are alarmingly clear: The attacks are becoming far more frequent, and they are getting deadlier.

We’ve studied every public mass shooting since 1966 for a project funded by the National Institute of Justice, the research arm of the U.S. Department of Justice. Our research spans more than 50 years, yet 20% of the 164 cases in our database occurred in the last five years. More than half of the shootings have occurred since 2000 and 33% since 2010. The deadliest years yet were 2017 and 2018, and this year is shaping up to rival them, with at least 60 killed in mass shootings, 38 of them in the last five weeks.