Sociologists have put people into different categories, based on socioeconomic factors, such as wealth, income, race, education, ethnicity, gender, occupation, social status, or derived power (social and political). They called this classification social stratification. Stratification is the relative social position of people within a social group, category, geographic region, or social unit.[1][2][3]
In modern Western societies, social stratification is defined in terms of three social classes: an upper class, a middle class, and a lower class. Each class is divided in three again: an upper, a middle, and a lower layer, or statum.[4] Moreover, a social stratum can be formed upon the bases of kinship, clan, tribe, or caste, or all four.
Socieieties that are based on states, that have more than one center, or that have a feudal hierachy use social stratification. In feudal society, there is nobility, and there are the common people, or peasants. Social scientists still argue about when social stratification first appeared: Either it started in the hunter-gatherer, tribal, and band societies or with agriculture and large-scale means of social exchange.[5] Determining the structures of social stratification comes from inequalities of status among people.The degree of social inequality determines a person's social stratum. Generally, the greater the social complexity of a society, the more social stratification exists, by way of social differentiation.[6]
Stratification can yield various consequences. For instance, the stratification of neighborhoods based on spatial and racial factors can influence disparate access to mortgage credit.[7]
People and groups or categories of people also move between the layers of the system. This movement can occur within one generation, or from one generation to the next one.
Mobility is sometimes used to classify different systems of social stratification. Systems that allow such mobility, or that make it easier are called open. Uually, they make movement possible by placing value on the achieved status characteristics of people. The societies with the highest levels of intragenerational mobility are considered to be the most open and malleable systems of stratification.[6] Those systems in which there is little to no mobility, even on an intergenerational basis, are considered closed stratification systems. For example, in caste systems, all aspects of social status are ascribed, such that one's social position at birth persists throughout one's lifetime.[9]