"Group grievance" radicalization dynamics are similar to those that are primed by personal grievances; the difference is that the subject perceives harm inflicted on a group that she belongs to or has sympathy for. This pathway accounts for the larger portion of political and ethnic radical violence, in which action is taken on behalf of the group at large rather than as an act of personal revenge. Radicalization out of sympathy for an outgroup is rarer, but can be observed in the Weather Underground's attempted alignment with the Black Panthers and Viet Cong. The tie between radicalization into violent extremism through group grievance and suicide bombing has also been quantifiably demonstrated: perceived threats to proximal identity such as the presence of foreign troops or invasion accounts for the majority of suicide bombings.