Understanding Trends in Occupational Sex Segregation By Daniel Guinea-Martin Advanced Centre for Scientific Research, Spain (formerly at the Office for National Statistics, UK) Presented at the Research Methods Festival, Oxford University 1 st July 2008

Introduction: Aims and scopes Substantive scope: To study occupational sex segregation / occupational mobility in the 1990s How? Complementing Census-based indices of segregation (Blackwell and Guinea-Martin 2005) with longitudinal research of one cohort born in the late 1950s: NCDS A similar cohort from the ONS Longitudinal Study

Introduction: Aims and scopes Methodological aims: –To assess the effect of attrition on representativenes –To assess ‘founding’ assumption

LS Structure Core Table Contains basic variables for ‘time constant’ characteristics (sex, decade of entry to or exit from the dataset…) Around 1 million individuals Core Table Contains basic variables for ‘time constant’ characteristics (sex, decade of entry to or exit from the dataset…) Around 1 million individuals Census- based tables Four time points / Four tables: Around 500,000 individuals each year Census- based tables Four time points / Four tables: Around 500,000 individuals each year Events tables Continuous since 1971 until present Examples: Births to sample women Infant Deaths Widow(er)hoods Cancer registrations Deaths…. Events tables Continuous since 1971 until present Examples: Births to sample women Infant Deaths Widow(er)hoods Cancer registrations Deaths…. Hypothetical example of data from the ONS Longitudinal Study core number 1Census-based variables (for example, of 1991 and 2001) core number 1Variables related to birth of 1st son in 1992 core number 1Variables related to birth of 2nd son in 1996 core number 2Census-based variables core number 3Census-based variables core number 3Variables related to emigration from the LS core number 4……. Key programming tool: Indexing commands, e.g. [i], [i+1]…

NCDS Structure NCDS Sweep 6 (2000) NCDS Sweep 5 (1991) Work- histories database (from 1974 onwards) - Combines restrospective information from NCDS5 & NCDS6 Work- histories database (from 1974 onwards) - Combines restrospective information from NCDS5 & NCDS6 Key programming tool: loops, e.g. - foreach i in 1/25 {do whatever} - Hypothetical example of data from NCDS data Start Job1…… Start Job 25 End Job 1…… End Job 25 Member 1…………………………………………………………………. Member 2…………………………………………………………………. Member 3…………………………………………………………………. Member 4…………………………………………………………………. Member 5…………………………………………………………………. ………………………………………………………………………

A methodological auto-biography The challenge: 1 st serious research experience with complex and ‘messy’ longitudinal data Easy to be surprised. Examples: –Supposedly time-invariant variables like sex or ethnicity might actually change across waves. –Easy to mistake ‘past’ variables for ‘current’ variables in life histories. –Easy to forget harmonising variables which categories change over time. –Different ways of storing variables in different tables and across time (e.g., numeric, string with trailing spaces…)

Survival kit Read the documentation very closely, particularly the questionnaires. Learn serious programming in one or two software packages: SPSS, Stata, R… Keep the syntax of all the transformations you operate on the data in strict sequence. In the syntax include comments on what you are doing and what you have found out about the data

Occupational sex segregation: Standardised Gini indices for the period (CO70) (CO80) (SOC90) (SOC90) (SOC2000) (SOC90) Census LFS ONS LS (no person imp.) Source: Blackwell, L. and D. Guinea-Martin (2005) ‘Occupational segregation by sex and ethnicity in England and Wales, 1991 to 2001’, in Labour Market Trends, Vol. 113, No. 12, pp

Occupational sex segregation in the NCDS & LS50s

What are these indices of segregation? Example: The Segregation Curve for NCDS 2000 Distance=D Gini=A/(A+B ) Male/female ratio

How to calculate the indices Index of dissimilarity Gini coefficient

Decomposing segregation: Theil’s index Theil’s entropy index of segregation (H) is a multi-group measure of segregation Allows the incorporation of various dimensions, for example employment status (full time vs. part time) or age groups Currently working on these dimensions to disaggregate the changes in occupational sex segregation during the 1990s

Theil’s entropy index of segregation ‘Entropy’ or diversity Theil’s index Decomposition of Theil’s H

Example: Decomposition of segregation among ISCO-88 occs in UK

Occupational sex segregation in the NCDS & LS50s

Occupational sex segregation for various quasi-cohorts in the 1990s

Occupational movers and stayers

Transitions across sex-typed occupations (occupational movers only)

Transitions across sex-typed occupations and non-work

Transition tables across SOC90 Major Groups and NIW: NCDS women (cell percentages)

Loglinear modelling of transition tables (men)

Transitions with greatest effect in the lack of fit of Model 2 (St.Residual>=|1.96|) Transitions with more NCDS men and fewer LS50s men than expected Transitions with more NCDS women and fewer LS50s women than expected Managers to Managers Associated Professionals to Associated Professionals Professionals to Professionals Associated Professionals to Associated Professionals Personal to Personal Transitions with fewer NCDS men and more LS50s men than expected Non-work to: Personal Nonwork Transitions with fewer NCDS women and more LS50s women than expected None Notes: Only transitions with n>=50 in each dataset are included Sources: Authors’ analysis. ONS Longitudinal Study and NCDS

Bibliography Blackburn, R et al (2001) ‘Occupational stratification’, in Work, Employment and Society, 15(3): Blackburn, R. and J.Jarman (2005) ‘Segregation and inequality’. GeNet Working Paper No.3 Blackwell, L. and D.Guinea-Martin (2005) ‘Occupational segregation by sex and ethnicity in England and Wales, 1991 to 2001’, Labour Market Trends, 113(12): Elliott, J. (2005) ‘Comparing occupational segregation in Great Britain and the United States’, Work, Employment and Society, 19(1): Gilbert, N. (1981) Modelling Society. And introduction to loglinear analysis for social researchers. London: George Allen&Unwin Guinea-Martin, D. and J. Elliott (2008) ‘Economic position and occupational segregation in the 1990s’, Centre for Longitudinal Studies Working Paper James, D. and K.E.,Taeuber (1985) ‘Measures of segregation’, in Sociological Methodology, 15: 1-32 Ramson, M.R. (2000) ‘Sampling distributions of segregation indexes’, Sociological Methods and Research, 28(4):