Social change refers to alterations in a society's social order, institutions, behaviors, or relations. Factors that can influence social change include natural elements, geography, demographics, economics, culture, and technology. Cultural lag describes a situation where technological or social changes occur more rapidly than a culture's rules and norms can adapt. Social classes are groups that occupy similar positions in a society's economic system of production, divided by social and economic status. The main social categories include the underclass, working class, middle class, and upper class.