A broad dichotomy in the study of occupational stratification, which correlates with many social indicators such as income, health, and educational attainment, as well as conditions of employment broadly defined. It is, nevertheless, based on a value-judgement about the status and nature of different occupations in the working class and the middle class, according to the amount of mental (non-manual) as opposed to physical (manual) labour they are supposed to require. A closely related distinction is that between blue-collar and white-collar work. Although widely institutionalized in everyday life and in law, attempts to reach agreed operational definitions of manual and non-manual work reveal that the distinction tends to be arbitrary. This is well illustrated by considering gender differences in occupational position: women doing mental work in white-collar jobs tend not to be accorded either the same pay or prestige as white-collar men. Ambiguity has not prevented sociologists themselves from identifying and describing broad inequalities of life-chances, life-style, and prestige as being associated with so-called manual/working-class and non-manual/middle-class occupations. More sophisticated classifications now used in the sociology of stratification attempt simply to reflect the subjective value element which samples of lay judges themselves employ to distinguish the prestige of jobs; however, the idea that there is a consensus in society about the relative worth of manual or mental labour is itself not borne out by empirical research. See also Goldthorpe class scheme; new working class; occupational classification; occupational prestige.