It seems to be taken in account. From the article: "Thus, although the most common fatality rate per event was 1 (48% of cases), in rare cases the ‘butcher bil

It seems to be taken in account. From the article: "Thus, although the most common fatality rate per event was 1 (48% of cases), in rare cases the ‘butcher bill’ could run into hundreds (less than 1% of events had a fatality rate of 100 or more). As a result, the rare but bloody events have a disproportionate effect on the trajectory. A good example of this effect is the latest ‘peak’ in the trajectory (during the 1990s) – it is entirely due to 168 deaths associated with a single event, the 1995 Oklahoma City bombing."