The political and social systems vary greatly in different regions, and allegiance is uniformly paid to the large urban centre in the area, rather than to a singular centralized authority. Each town has a leader (Oba), who may achieve his position in several different ways including inheritance, gaining the position through participation in title associations, or being personally selected by an Oba already in power. Every Oba, however, is considered to be a direct descendant of the founding Oba in each city. A council of chiefs usually assists the Oba in his decisions. Title associations, such as the ogboni, play an important role in assigning and balancing power within the cities.