Occupational Gender Segregation Index
Also known as: Duncan Dissimilarity Index, Index of Dissimilarity, Sex Segregation Index
Occupational gender segregation indices measure how unevenly women and men are distributed across occupations. The most widely used is the Duncan and Duncan index of dissimilarity, introduced in 1955, which gives the share of women (or men) who would have to change occupations for the two distributions to match. Together with margin-free alternatives and decompositions into horizontal and vertical components, these indices are the standard tools for quantifying the sex segregation of labour markets.
Key highlights
- The dissimilarity index has a direct, intuitive interpretation as the share who would have to switch occupations to equalise distributions.
- Computable from standard sex-by-occupation employment tables available in most labour statistics.
- Extends to margin-free and size-standardised forms that support valid cross-national and over-time comparison.
- Decomposable into horizontal and vertical components that separate difference from hierarchy.
Intuition
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How it works
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When to use it
Use occupational segregation indices to measure and compare the extent to which women and men work in different jobs, to track changes over time, and to study the link between segregation and the gender pay gap. They are well suited to descriptive and comparative labour-market analysis. Use margin-free variants and decompositions when comparing across countries or periods with different occupational structures or female participation, and be cautious treating a single dissimilarity value as comparable across studies using different occupational classifications.
Strengths & limitations
- The dissimilarity index has a direct, intuitive interpretation as the share who would have to switch occupations to equalise distributions.
- Computable from standard sex-by-occupation employment tables available in most labour statistics.
- Extends to margin-free and size-standardised forms that support valid cross-national and over-time comparison.
- Decomposable into horizontal and vertical components that separate difference from hierarchy.
- The basic dissimilarity index is sensitive to the occupational classification's granularity and to the marginal distributions.
- It is descriptive: it quantifies segregation but does not explain its causes or its consequences for pay.
- A single index can mask whether segregation is horizontal (difference) or vertical (hierarchy), which differ in normative significance.
- Comparisons across countries are fragile when occupational coding schemes are not harmonised.
Common pitfalls
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Applications
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Frequently asked
What does a dissimilarity index of 0.5 mean?
It means that half of women (equivalently, half of men) would have to move to a different occupation for women and men to be distributed identically across occupations. The index runs from zero, where the two sexes have the same occupational distribution, to one, where they share no occupations. The interpretation depends on the occupational classification used, so the categories should always be reported.
Why use margin-free indices instead of the simple dissimilarity index?
The simple dissimilarity index changes when the overall share of women in the labour force or the relative sizes of occupations change, even if the underlying tendency to segregate does not. Margin-free and log-multiplicative measures, such as those Charles and Grusky use, hold the marginals constant so that comparisons across countries and over time reflect genuine differences in segregation rather than differences in labour-force composition.
What is the difference between horizontal and vertical segregation?
Horizontal segregation is the tendency for women and men to work in different occupations that are not necessarily ranked — for example nursing versus carpentry. Vertical segregation is concentration at different levels of a hierarchy, with one sex over-represented in higher-status, better-paid positions. The same overall index value can reflect very different mixes of the two, and only the vertical component maps cleanly onto inequality, which is why decomposition matters.
Sources
- 1.Duncan, O. D., & Duncan, B. (1955). A methodological analysis of segregation indexes. American Sociological Review, 20(2), 210–217.
- 2.Charles, M., & Grusky, D. B. (2004). Occupational Ghettos: The Worldwide Segregation of Women and Men. Stanford University Press.ISBN 9780804748803
- 3.Blackburn, R. M., Jarman, J., & Brooks, B. (2000). The puzzle of gender segregation and inequality: A cross-national analysis. European Sociological Review, 16(2), 119–135.
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Cite this page
ScholarGate. (2026, June 22). Occupational Gender Segregation Index. ScholarGate. https://scholargate.app/gender-studies/occupational-gender-segregation-index