Natives of the Pacific Northwest were economically successful, which led to their highly structured society. Because resources were plentiful and survival was relatively manageable, their surplus of goods and time led to an obsession with personal acquisition and the class system that resulted from such affluence. The class structure of the Northwest natives primarily distinguished between slaves and freemen. Slaves were usually taken in raids on foreign villages and occasionally as payment for outstanding debts. The treatment of slaves varied among regions. Most were allowed to marry, but the children of slave unions were automatically enslaved. Freemen were carefully ranked, based upon a combination of wealth and heredity; this ranking was publicly re-confirmed at community events. There was a limited amount of mobility between ranks for those who developed a special skill or killed a titled man in a raid, for example. Some communities further divided the class of freemen into nobles and commoners. Those born into prestigious families gave potlatches and accumulated material wealth in the form of blankets, baskets, hides, canoes and slaves, became nobles. Nobles frequently were distinguished by a familial crest, unique name or song. Pacific Northwest communities were highly organized. They were presided over by an aristocratic chief who inherited his position matrilineally. Chiefs employed assistants to perform all public-speaking duties so that they were spared the disgrace of addressing commoners. The village's economic activity was planned and delegated by the senior men and older matrons to ensure efficient use of resources. Family units exerted a large impact on social organization. Extended families shared residences and each house designated a male leader who inherited his authority from his mother's brother. Elders carefully arranged marriages. Virgin brides were highly prized; some parents confined their daughters to a boarded-off room in the house from the onset of puberty until marriage. The resulting assurance of virginity—and unusually light skin—were likely to command a high price. The price, a fixed amount paid to the parents of a man's future bride, reflected the social prestige of the bride and groom. Certain Northwest tribes favored marriage between first cousins, while polygamy flourished in wealthier tribes.