Stratification is a term used to characterize a structure of inequality where (a) individuals occupy differentiated structural positions and (b) the positions are situated in layers (or strata) that are ranked hierarchically according to broadly recognized standards. The implied reference to sedimentary layers from geology reflects the relative permanence of the posited structure and the long history that is assumed to have generated it. Stratification researchers focus primarily on the empirical study of (a) the sources of the rankings that generate the hierarchy of strata, (b) the mobility of individuals between strata, and (c) the mechanisms of integration that allow societies to cope with the existence of persistent inequalities between strata.
The structural orientation of stratification scholarship can be contrasted with distributional approaches to the study of inequality that have dominated economics. Modelling the distribution of valued resources across individuals makes possible explanations of change in response to short-run interventions and shocks from unforeseen exogenous events. For stratification researchers, short-run variation in inequality is considered to be noise that dissipates as social inequalities are reproduced.
The development of the concept of stratification
Although the sociologist Pitirim Sorokin is often credited with first developing and then using the concept of stratification in empirical work, the clearest lineage emerges in the work of Talcott Parsons and that of his students. In his essay ‘An analytical approach to the theory of social stratification, Parsons (1940, p. 841) wrote: ‘Social stratification is regarded here as the differential ranking of the human individuals who compose a given social system and their treatment as superior and inferior relative to one another in certain socially important respects.’ Parsons (1940, p. 849) then wrote that the ‘status of any given individual in the system of stratification in a society may be regarded as a resultant of the common valuations underlying the attribution of status to him’ in dimensions such as achievements, possessions, authority, and power.
In 1945 Parsons’s students, Kingsley Davis and Wilbert Moore, wrote ‘Some principles of stratification’ in which they specified a clear (but ultimately controversial) conception of the sources and inevitably of stratification. Adopting the functionalist framework championed by Parsons, Davis and Moore maintained that society is a functioning social system, directly analogous to a living organism, which survives because it determines necessary social positions, recruits appropriate individuals to fill each position, and induces individuals to perform their assigned duties. To foster efficiency, the social system attaches differential rewards to alternative positions, where the sizes of the rewards are based on (a) the functional importance of the position to the society as a whole and (b) the counterfactual scarcity of individuals willing to take the position in the absence of appropriate rewards. Davis and Moore (1945, p. 243) claimed that ‘Social inequality is thus an unconsciously evolved device by which societies insure that the most important positions are conscientiously filled by the most qualified persons.’ (As discussed later, this view of the sources, functional necessity, and inevitably of stratification was challenged almost immediately by scholars wishing to focus on the mutability of the structure of inequality as well as the power dynamics that pervade it.)
Thirteen years after his initial essay on the topic, and eights years after the seminal Davis and Moore piece, Parsons (1953, p. 92) began ‘A revised analytical approach to the theory of social stratification’ with the bold assertion: ‘It has come to be rather widely recognized in the sociological field that social stratification is a generalized aspect of the structure of all social systems, and that the system of stratification is intimately linked to the level and type of integration of the system as a system.’ Parsons then discussed how societies cope with the functional necessity of stratification by developing norms and value standards that, by and large, attribute differences in attainment to differences in achievement.
Parsons and his colleagues assumed that moderately high levels of intergenerational mobility are essential for the efficiency and integration of society. Functionally important positions must be staffed by the most qualified individuals and hence based on past achievements rather than social origins. And, to ensure integration and social order, reward for achievement rather than reward for social origins must be reasonably expected and then observed. In later work, Parsons (1959) specified the social processes that develop and then transmit these norms of achievement in his essay ‘The school class as a social system’. He argued that schools serve two primary functions in society – socialization and allocation – which they fulfil in a simultaneous four-part process: (a) emancipation of children from exclusive attachment to their parents, (b) inculcation of values and norms that cannot be taught by parents, (c) differentiation of the school class on actual achievement and on differential valuation of achievement, and finally (d) an allocation of individuals to positions in the adult role system. Parsons (1959, p. 145) wrote:‘Differentiation of the class along the achievement axis is inevitably a source of strain, because it confers higher rewards and privileges on one contingent than on another within the same system. … [The] common valuation [of achievement] helps make possible the acceptance of the crucial differentiation, especially by the loser in the competition.’ As a result of this scholarship, the term ‘stratification’ gained popularity in sociology, becoming the name for the entire sub-field of inquiry concerned with the causes and consequences of inequality. Thereafter, the term diffused throughout the social sciences and was drawn upon by historians and anthropologists to frame comparative studies of inequality. Within economics, the term has been used less frequently and with no consistent definition. For early studies of racial–ethnic inequality, one can find the term used in the dissimilar work of Closson (1896) and Myrdal (1944). More recently, the term has been used to refer to the determinants of labour market earnings that arise from family background rather than one’s own skills (see Heckman and Hotz, 1986). For Durlauf (1994) and Benabou (1996), the term is used to refer to persistent neighbourhood differences in average levels of family income and well-being.
Complexity and contention
The foregoing presentation of the Parsonian perspective on stratification is sanitized in two important respects. First, it ignores alternative perspectives which rejected the Parsonian vision at the time it was being proposed and which later grew into the neo-Marxist scholarship of the 1960s onward. This scholarship led Pierre Bourdieu (1984, p. 245) to look back at the stratification literature of the 1950s and 1960s and declare that ‘the opposition between theories which describe the social world in the language of stratification and those which speak the language of class struggle corresponds to two ways of seeing the social world.’Second, the presentation overly formalizes what for some was an informal term, often used as shorthand for the simple notion of a systematic pattern of inequality. In fact, many of the scholars who worked within the stratification tradition used a mixture of class-based and stratification-based terminology in the course of the empirical analysis that was their main interest. For example, Sorokin (1927, p. 11) wrote: ‘Social stratification means the differentiation of a given population into hierarchically superposed classes.’ Edward Shils (1962, p. 249) wrote: ‘The class system, or the system of stratification of a society, is the system of classes in their internal and external relationships.’ And Melvin Kohn (1969, p. 11) wrote: ‘we use a multidimensional index of class, based on the two dimensions of stratification that appear to be the most important in contemporary American society – occupational position and education.’
Empirical mobility research in sociology and economics
The most important legacy of stratification research is the empirical study of mobility between strata, however defined. Mobility researchers have comprehensively modelled rates and patterns of intergenerational and intra-generational movement between strata (see Morgan, Grusky and Fields, 2006, for a review and examples from both sociology and economics). Two approaches to mobility have dominated sociology. In the first, mobility is modelled by accounting for movement between aggregated occupations, sometimes labelled social classes. Accordingly, intergenerational mobility is analysed via inspection of cross-classifications of parents’ and children’s occupations. In the early literature, levels of mobility were summarized by alternative indices, often derived in the course of analysis of cross-classifications drawn from different societies. The later literature dispensed with mobility indices, focusing instead on the fine structure of patterns of mobility using new log-linear modelling techniques.
With the publication of Blau and Duncan’s American Occupational Structure in 1967, a second approach to the study of mobility reached maturity in sociology, later labelled status attainment research. In this tradition, sociologists focus on the causes and consequences of differences in socio-economic status (often defined in terms of scores attached to occupational titles, based on the average educational attainment and earnings of incumbents). Levels of social mobility are measured by intergenerational correlations of socio-economic status, and these correlations are then decomposed with the use of intervening variables in structural equations models.
An important concern of this literature has been the impact of structural change over time on mobility outcomes and hence the extent to which such change has altered the stratification order. In particular, the degree to which shifts in occupational distributions generate upward mobility has been studied extensively. Such outcomes were welcomed in the middle of the 20th century, and elaborated in scholarship where it was argued that the growth of higher-status occupations is an inevitable outcome of the process of industrialization (and also, by implication, that Marxist claims of the inevitability of class polarization under capitalism had been exaggerated). Perhaps reflecting the growing pessimism and radicalism of sociology in the 1960s and 1970s, such structurally-induced upward mobility was deemed less theoretically meaningful than levels of mobility purged of these effects. The study of what came to be known as pure exchange mobility then became possible with the development of log-linear modelling techniques that could be used to ascertain margin-free measures of mobility. This work is best represented by the cross-national research of Erikson and Goldthorpe (1992), which supported the claim that industrialized societies can be characterized by broadly similar patterns of intergenerational occupational mobility (in spite of national mythologies that claim that some societies are more open and meritocratic than others).
In economics, mobility has been a topic of theoretical and empirical work as well, even though it is not connected directly with any tradition of stratification research in sociology. Rather, the early work arose out of labour economics, based on the ‘unified approach to intergenerational mobility and inequality (Becker and Tomes, 1979, p. 1154), which brought together human capital theory with dynastic investment models for family behaviour. As with the status attainment tradition in sociology, economists working in this area often seek single-number expressions for levels of mobility, generally intergenerational correlations of income (although estimated as elasticities from regressions of log earnings across generations; see Solon, 1999). In contrast to the sociological literature, economists have argued recently that there are substantial cross-country differences in mobility, with greater intergenerational mobility of earnings in mainland Europe than in either the United States or the United Kingdom (see Solon, 2002). In addition to the large economics literature on earnings mobility, a well- developed literature on the intergenerational dynamics of wealth inequality now exists (see Mulligan, 1997; Charles and Hurst, 2003).
Economists have begun to focus, like sociologists, on categorical representations of the structure of inequality, examining placement within the distribution of earnings and wealth (using either fixed categories across generations or relative ranks within distributions). When analysed as cross-classifications of quantiles, these methods are similar in spirit and method to the between-social-class mobility studies of sociology. In fact, Björklund and Jäntti (1997) refer to income groups as income classes, and reference the log-linear tradition of mobility research in sociology.
Economists have also become interested in the extent to which increasing inequalities within the labour markets of industrialized countries between the 1970s and the 1990s can be seen as less consequential to the extent that they have been accompanied by increasing chances of intergenerational mobility (see Welch, 1999). Relatedly, some economists have sought to determine the extent to which increasing chances of upward mobility sustained support for the market reforms in eastern Europe and the former Soviet Union that increased inequality (see Birdsall and Graham, 2000). This work is reminiscent of the concern with societal integration that is most closely associated with Parsons in sociology, and it may represent a shared territory which both sociologists and economists will further cultivate.
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Uncorrected proof from The New Palgrave Dictionary of Economics 2nd edition. Edited by Steven Durlauf and Lawrence Blume. Published by Palgrave Macmillan. Forthcoming.
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