There is a US mass murder chart by year that pops up occasionally. You can see two things. 1) the highest year on the chart has a run and a pause at the end. 2) The right side of the chart seems too narrow. 16 years is enough to capture not necessarily outliers, but at least a high year that doesn't flatline at the end. Does mass murder mean revert? Maybe as a result of being sped up and burnt out by social transmission like a fast disease?