1. Quantitative methods for researching lives through time Heather Laurie Institute for Social and Economic Research University of Essex laurh@essex.ac.uk

2. Overview What do we mean by longitudinal? Distinguish method from design Cohort and panel designs What can quantitative longitudinal studies tell us? Introduce a new study – Understanding Society

3. Defining ‘longitudinal’ Term that encompasses many forms of data and many designs Used as a catch-all for any study that has some element of time within it From oral histories through to qualitative analysis of life-course events and transitions And to quantitative panel or cohort analysis of repeated observations of the same cases

4. Defining ‘longitudinal’ Who or what are we following? For what time period? How often?

5. Defining ‘longitudinal’ Common factors regardless of methodology Information at or about more than one point in time Research questions that are inherently longitudinal in nature  understanding the antecedents of events  process and lived experience  influences on decision-making  the timing of transitions from one state to another

6. A longitudinal research focus Inherently longitudinal research questions e.g.  Educational and employment outcomes for children depending on family and social background  Labour market transitions and the impact on life time earnings, career progression and well-being  Impact of ethnicity and gender on long-term outcomes in the labour market and family life  Inter-generational transmission of attitudes, values, deprivation, wealth

7. Analysis across the life-course A longitudinal perspective on change in individuals’ lives over time Recognises complex interactions between life course domains e.g. work, living arrangements, income, leisure, health Importance of social context e.g. household, wider social networks, local environment, and social and cultural norms.

8. Method or design? The design of any study depends on the research questions you want to answer The method you use to collect those data depends on many elements  cross-sectional or longitudinal  the population of interest  generalisation to a population vs case study  the type of analysis needed to answer your research questions

9. Quantitative design approaches Retrospective studies  Past events and transitions are recalled by respondents e.g. life time employment history Record linkage panels  From data collected for administrative purposes e.g. taxation or social welfare system Prospective studies  Produce ‘waves’ or ‘sweeps’ of measurement collected over a period of years

10. Cohort studies Often birth cohorts e.g. MCS but can be any age group/ ELSA aged 50+ Follow up same cohort members at fairly long intervals - e.g. NCDS now every 4 years; ELSA every two years Birth cohorts include developmental data as well as social and economic data Triangulation of data from parents, teachers, schools associated with cohort member Allow observation of long-term outcomes with detailed information on childhood and family circumstances

11. Household panels Draw a sample at one point in time and follow those sample members indefinitely Collect individual level data in household context Usually interview all members of the household Repeated measures at fixed intervals (usually annual data collection) Annual data collection allows analysis of short-term change Indefinite life design allows longer-term outcomes to be observed

12. What do quantitative longitudinal panels offer? Temporal information on sequence of events Allows us to make better inferences about cause and effect Short term dynamics of change Long term dynamics Links between current events and outcomes and past history

13. What do quantitative longitudinal panels offer? Repeated observations on the same individual controls for the effects of unmeasured heterogeneity between cases Reduce recall error Can better understand social change by separating out age, period and cohort effects To establish the effect of a treatment Sampling techniques mean statistical findings can be generalised to the whole population

14. Understanding Society A new household panel for the UK Key features: Large sample size of 40,000 households Includes all of UK Household focus with full age range sample Annual interviews with all aged 10 and over Innovation Panel for methodological research and testing

15. Key features(cont) Multi-topic design to meet a wide range of disciplinary and inter-disciplinary research needs Ethnic minority research Biomedical research Data linkage to administrative records Opportunities for qualitative linked studies

16. Annual repeating content Basic demographic characteristics Changes between waves - employment, fertility, partnering, geographic mobility, health Health status (e.g. SF12), disability, Labour market activity and employment status, job search Current job characteristics, basic employment conditions, hours of paid work, second jobs Childcare, other caring within and outside household Income and earnings Life satisfaction Political affiliation – basic measures Transport and communication access Education aspirations and expectations Consumption expenditure Housing characteristics – basic Housing expenditure Household facilities, car ownership

17. Understanding Society rotating content Family and social networks outside the household Attitudes and behaviours related to environmental issues Illicit and risky behaviour especially for young people Psychological attributes Cognitive ability measures Health outcomes and health related behaviour Quality of sleep Well-being Quality of marital relationships Risk and trust Collection of data about younger children < 10 Transition into young adulthood Discrimination and harassment Ethnic and national identity

18. Ethnic minority research Boost sample for five key groups in the UK (Indian, Pakistani, Bangladeshi, Caribbean, Black African, Mixed) Increasing prominence of research into ethnic difference for understanding the make-up of UK society Focus on issues of diversity and commonality. Common questionnaire content across the sample for many questions Additional questionnaire content within the ethnic minority boost

19. Linkage to administrative records Ask respondents for permission to link to:  Health records and hospital episodes statistics  Education records  Pension and state benefit records Parents asked for permission on behalf of children < 16 Link to pupil level and school level education data  each pupil in England has a Unique Pupil Number so can follow as they progress through the school system Link survey data to a range of geo-coded data, including environmental data

20. Biomedical research Collecting a wide range of biomarkers and health indicators Opportunity to assess: exposure and antecedent factors of health status, understanding disease mechanisms (e.g. gene- environment interaction), household and socioeconomic effects, analysis of outcomes using direct assessments or data linkage. Opens up prospects for advances at the interface between social science and biomedical research.

21. Research potential Developed as a research resource for the whole user community First data available from the UK Data Archive from early 2011 Like the British Household Panel Study(BHPS), we hope it will be widely used

22. ISER publications and web contact For further information about Understanding Society see www.understandingsociety.org.ukwww.understandingsociety.org.uk For ISER publications and Working Papers see www.iser.essex.ac.uk/publications www.iser.essex.ac.uk/publications