Life expectancy by NS-SEC Structure, technical and conceptual issues and results BSPS 8 Sept 2011 Brian Johnson ONS Health & Life Events Division Newport

Introduction Why life expectancy by NS-SEC? What is NS-SEC and how is it derived? Why is the ONS Longitudinal Study vital to this analysis? Main technical problems and approach to them Conceptual concerns Summary results

Background ONS has produced life expectancy by Registrar General’s social class (RGSC) for the period In 2001 RGSC was replaced by NS-SEC for official statistics Need to produce life expectancy by NS-SEC This is how it was done

Registrar General’s social class Non-manual I Professional II Managerial and technical IIIN Non-manual skilled Manual IIIM Manual skilled IV Manual semi-skilled V Manual unskilled

Life expectancy at birth by social class, for male & females, England and Wales, Non- manual vs Manual Source: ONS Longitudinal study MalesFemales

What is NS-SEC? Socio-economic classification based on occupation Conceptually based on ‘employment relations’ Job security/prospects/autonomy ‘service contract’ relationship ‘labour contract’ relationship

NS-SEC operational and analytical categories Source: Rose D and Pevalin D (ed) (2003) A Researcher’s Guide to the National Statistics Socio-economic Classification.

Part of NS-SEC derivation matrix 1.1Employers in large organisations and higher managers 1.2Higher professional occupations 4Self-employed and own account workers 2Lower managerial and professional occupations Source: ONS (2002): The NS-SEC User Manual

Life Table (illustrative)

Period and Cohort Life expectancy Period life expectancy (shown here) reflects mortality rates prevailing at all ages during calendar period to which it refers Therefore ‘life expectancy at birth’ for child born in 2004 is the number of years that child could expect to live if age-specific mortality rates stayed as in 2004 Cohort life expectancy allows for anticipated future changes in mortality rates – projection implies element of subjectivity

LS Structure 1971 Original sample: 530,000 members; selected from 1971 Census 1971 Original sample: 530,000 members; selected from 1971 Census ,000 sample members found at 1981 Census ,000 sample members found at 1981 Census ,000 sample members found at 1991 Census ,000 sample members found at 1991 Census ,000 sample members found at 2001 Census ,000 sample members found at 2001 Census Entries New Births 272,000 Immigrations 174,000 Entries New Births 272,000 Immigrations 174,000 Exits Deaths 239,000 Embarkations 40,000 Exits Deaths 239,000 Embarkations 40,000 Events: Births to sample women 260,000 Births to sample men 49,500 Infant Deaths 2,200 Widow(er)hoods 82,000 Cancer registrations 114,000

What can the LS offer the study of life expectancy by social classification? Based on census returns and administrative sources – low levels of ‘attrition’ (compared with survey data) Can attribute social indicator (eg. social class/occupation) several years before death – no need to rely on death registration Eliminates numerator-denominator bias - uses actual person-years at risk as denominator

Hierarchy for assignment of socio- economic class

Person-years at risk

Members’ Occupation/emp status at census 81,91,01 Non-members’ Occupation/emp status at census 81,91,01 New births 80’s,90’s,00’s Father/mother Occ/emp status NS-SEC Classifica -tion program Deaths & Pyrs program Age-specific mortality rates Life Tables NS- SEC D E R I V A T I O N M A T R I C E S Cancelled Ciphers Structure of Life Expectancy by NS-SEC project Own NS-SEC Father’s Mother’s Spouse’s NS-SEC Father’s Mother’s NS-SEC At birth NS-SEC80 Derivation Matrix project Losses to Follow up

Components of the project 1.Construct “NS-SEC80” derivation matrix using 1981 occupational classification and employment status to produce (reduced) NS-SEC classification for 1981 Census 2.Construct ‘own’ NS-SEC at each census where present 3. Construct father’s, mother’s and spouse’s NS-SEC at 1981, 1991 & 2001 censuses where present, using LS non-members file 4. Construct father’s and mother’s NS-SEC for 1980’s, 1990,s and 2000’s new births 5. Construct hierarchical scheme for assigning ‘sec’ to each LS member, using own or father’s, mother’s, or spouse’s class 6. Adapt rule-based programs to obtain age-specific mortality rates by NS-SEC

NS-SEC90 analytic classes– using SOC90

Technical issues No one-to-one mapping of CO80 to SOC90 There is a bridge coding which applies to both 1981 and 1991 But 1981 Census occupations not classified by it!

46% CO80 SOC90 16% 38% Comparability of OPCS CO80 occupation codes and SOC90 unit groups Source: OPCS (1991) “Standard Occupational Classification”, Volume 3, HMSO

Solutions Map those occupations which have exact or near-exact linkage Add other occupations which are not uniquely linked but map to the same standard NS-SEC analytic groups Use empirically based rules to estimate the rest (approx 3% of population)

Part of NS-SEC80 derivation matrix NS-SEC analytic classes

Validation – cross-tab of 1993 deaths

Conceptual problem NS-SEC was designed for the economic structure of 2000 not 1980 May be criticised as conceptually invalid But empirically, it works!

Period life expectancy – males at birth Source ONS Longitudinal Study

Period life expectancy – females at birth Source ONS Longitudinal Study

Period life expectancy – men aged 65 Source ONS Longitudinal Study

Period life expectancy – women aged 65 Source ONS Longitudinal Study

Summary ONS has a series of trends in life expectancy by (RG) social class Has now developed a series by NS-SEC also using the ONS Longitudinal Study (published Feb 2011*) Similar pattern of socio-economic gradient apparent in results *For full description of methods and context of results see Health Statistics Quarterly volume 49 national-statistics-socio-economic-classification /health-inequalities-in-the-21st- century.pdf