What is the ONS Longitudinal Study? (2)

What data does the LS contain?

The data in the LS come from complete census returns from 1971 onwards, linked with vital event data from various sources. The census data in the LS, which is available for both LS members and the people they live with, include the following:

Age, sex, marital status
Family, household or communal establishment type
Housing, including tenure, rooms and amenities
Country of birth, and (in 1971) parent's country of birth
Ethnicity (1991 & 2001)
Educational qualifications
Economic activity
Occupation and social class
Migration and travel to work
Long-standing illness (1991 & 2001) and self-rated health (2001)
Religion (2001)
Caregiving (2001)
Marriage and fertility history (1971)

Copies of the census forms used to collect these data are available for download here.

The events data linked to LS members' census records mean that the data set also includes information on:

Fertility (live and still births registered to women, and to men for the period 1971-78 and 1981 only)
Infant deaths (deaths of infants born to sample mothers)
Cancer registrations
Mortality (deaths of sample members), including full information from registration forms, such as cause of death
Widow(er)hoods (deaths of sample members' spouses)

As an example, consider this timeline which shows census and event data recorded for an hypothetical LS member.

An overview of the structure of the LS is available (PPT 42K), showing the different types and numbers of events linked into the study.

What has it been used for?

The list below shows the various research areas in which the LS has been used. Click on an item in the list to see a list of publications in that research area.

You could also view a presentation: Academic research using the ONS Longitudinal Study by Emily Grundy, March 2007 (PowerPoint 765K).

How does it compare to other data sets?

One of the major strengths of the ONS Longitudinal Study is its size. It represents 1% of the population of England and Wales, with a sample of about 950,000, and covers over 30 years of census and event records. This combination of large sample size and long follow-up time makes it unique. For studies in certain areas, such as ethnicity, the LS is the only longitudinal study large enough to give statistically useful sample sizes. Other important advantages are that the data set includes information on co-residents of LS members as well as the members themselves, and information on people in communal establishments, who are excluded from most national surveys. Census coverage rates and the linkage and trace rates obtained in the LS compare very favourably with response rates achieved in surveys.

Its main limitation is the relatively restricted range of variables available. For example, there is no information on smoking or on income. It is not possible to go to the sample and gather information on extra variables, as is sometimes the case when dealing with surveys. However, it is possible to link information on the characteristics of areas that LS members live in (for example, deprivation score of the ward of residence). The LS is also restricted to England and Wales, though a Scottish LS exists and guidance is being developed for comparative research. A Northern Ireland Longitudinal Study has recently been launched.

For certain studies, another data set may be more suitable than the LS. Some suggestions are provided below:

Longitudinal studies:

British Cohort Studies:
1946 (MRC National Survey of Health and Development): cohort of 5,362 births in 1946 followed up to the present day. Contains data on subjects' physical and mental health, including observational measures, diet and lifestyle, and family, employment and social circumstances.
1958 (National Child Development Study): cohort of 17,000 births in 1958 followed up at intervals (most recently 2008-9). Contains a wide range of medical/health data.
1970: cohort of 17,198 births in the UK in the week 5-11 April, 1970 followed up to 2004. Contains medical data and data on physical, educational, social and economic development.
Millennium Cohort Study: began with a cohort of 20,000 births in the UK for a twelve month period from June 2001. The second sweep is now taking place with the children at around 3 years of age. Fieldwork started in September 2003 in England and Wales, and December 2003 in Scotland and Northern Ireland.
British Household Panel Survey: cohort of 5,500 households and 10,300 individuals in Great Britain, followed up from 1991 to (so far) 2007.

More information on these, and other longitudinal surveys, is available from the Keeping Track website at the Institute for Social and Economic Research (ISER) at the University of Essex.

Cross-sectional studies:

Samples of Anonymised Records (SARs): a 3% sample of census records at individual level, and a 1% sample at the household level, available separately for Great Britain and Northern Ireland from the 2001 Census.
General Household Survey: annual/near-annual survey based on a sample of around 10,000 private households in Great Britain (around 18,000 adults).
Health Survey for England: annual surveys with a common core of questions and specific modules with a different focus for each year. Questions asked and sample populations vary from year to year depending on the focus.
Labour Force Survey: a quarterly sample survey of 60,000 private households in Great Britain. Questions asked on respondents’ personal circumstances and their labour market status.

More information on these, and other national surveys, is available from the UK Data Archive, and the Economic and Social Data Service.

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