The chart in this infographic shows the long-term trend in “mass shootings” in the U.S. The FBI defines a “mass murder” as four or more murders during the same incident, with no distinctive time period between the murders. The chart shows those in which the murder weapon was a firearm.
Professor Fox extrapolated the “mass shooting” statistics from the FBI’s Supplementary Homicide Report. The most recent years are not shown due to the lagtime between when the incident occured and when the FBI concludes at least the preliminary investigation.
It is not known why the number of mass murders of any type varies so widely from one year to the next. However, because of the huge differences year to year, this chart can help keep one or several tragedies in context in light of the long-term trend.