Caste is a form of social stratification characterized by endogamy, hereditary transmission of a lifestyle which often includes an occupation, ritual status in a hierarchy and customary social interaction and exclusion based on cultural notions of purity and pollution. Its paradigmatic ethnographic example is the division of Indian society into rigid social groups, with roots in India's ancient history and persisting until today. However, the economic significance of the caste system in India has been declining as a result of urbanization and affirmative action programs. A subject of much scholarship by sociologists and anthropologists, the Indian caste system is sometimes used as an analogical basis for the study of caste-like social divisions existing outside India.