Social Organization. Chimbu society is organized around membership in agnatic kin groups with small groups at the lower level combining with other groups to form larger inclusive memberships, much like a segmentary lineage system. Individual loyalties and associations are generally strongest at the smallest, least inclusive level associated with common Residence areas and shared resources. The clan, the largest exogamous group, commonly acts as a unit in large ceremonial activities and does have a common territory. The largest indigenous sociopolitical organization is the tribe. The tribe, numbering up to 5,000 people, acts as a defensive unit in times of tribal fights with people from other tribes. The marriages contracted between members of different clans and tribes are fundamental in establishing political and economic relationships beyond the local level.
Political Organization. In traditional times the tribe was the largest political unit, but parliamentary democracy, begun in the late 1950s and early 1960s, created constituencies much larger than the traditional kin-based political units, but the influence of small local groups centered on leaders, called "big-men," has not diminished. These men are influential in organizing ceremonial exchanges of food and money, as well as rallying support for the candidacies of those standing for election. Typically more than one man from each tribal group stands in elections, fracturing support among many local candidates and allowing the successful candidate to win with often less than 10 percent of the total votes. In many ways modern parliamentary politics has not increased the scale of Chimbu political groups—even national-level politicians can gain office with a following not much larger than those supporting some traditional leaders in the past.
Social Control and Conflict. Although the possibility of violence, between family members as well as between large tribal groups, serves to control people's actions, mediation by third parties, often politically important men, is more often used to prevent or resolve disputes. Accusations of witchcraft are also levied against those who are perceived to be threatening agnatic group strength, usually against women, who marry into the group and are seen sometimes to have divided loyalties. Warfare occurs between different tribes and occasionally between clans within a tribe. Traditionally, the relations Between tribes were characterized by a permanent state of enmity, which served as an important contributing factor to the unity of a tribe. In the decades following colonial contact warfare at first diminished, only to reappear in the 1970s. Although the incidence of warfare is related to competition over scarce land, often the incident that precipitates fighting is a dispute over women, pigs, or unpaid debts.