Appendix: Methodology—Database Construction

Despite their atypicality, some nontraditional groups and individuals were included in the dataset. For example, the actions of the Unabomber were included because of a shared ideology, despite atypical methods. Similarly, the Sea Shepherd Conservation Society’s attacks were included because of shared tactics and ideology despite the fact that the group is not clandestine. For some groups, incidents were included on a case-by-case basis, as attack histories lacked a unity of purpose. For example, the Canadian group Direct Action carried out a number of attacks, only one of which was included in the dataset, as it was carried out with an environmentalist justification whereas other attacks were done for antimilitarist or feminist motivations. Actions were excluded from the dataset based on tactics and ideology. Incidents excluded from the dataset include demonstrations, planned confrontational actions (such as hunt saboteur expeditions), and attacks that claimed a justification that did not show explicit ideological linkages. For example, if the Hunt Saboteurs Association disrupted a fox hunt through physical blockade and confrontation of hunters, this incident was excluded, as it was not clandestine or utilizing tactics under examination, but if the same group used arson to target a hunter’s lodge, that act of arson was included. Similarly, the large series of clandestine vandalisms and sabotages carried out MICHAEL LOADENTHAL