Gangs began to develop during the shift from an agrarian to an industrial society. Gangs have evolved from scavenger and territorial gangs to organized, corporate gangs that operate as economic enterprises and that have strong leaders. The main focus of corporate gangs is participation in illegal money-making ventures. Drugs thus have become the same unifying economic force for juvenile and adult gangs today as alcohol was during Prohibition. Corporate gangs use physical and psychological intimidation in the selling of narcotics and the efforts to keep competition out of their business zones. The urban underclass provides an abundant source of labor for drug trafficking operations, and the gang imperialism that now exists represents a form of American capitalism.