About the LS

What is the LS?

The ONS Longitudinal Study is a complete set of census records for individuals, linked between successive censuses, together with data for various events. It relates to a sample of the population of England and Wales.

The sample comprises people born on one of four selected dates of birth and therefore makes up about 1% of the total population. The sample was initiated at the time of the 1971 Census, and the four dates were used to update the sample at the 1981,1991 2001 and 2011 Censuses and in routine event registrations. Fresh LS members enter the study through birth and immigration and existing members leave through emigration or death, however their data is retained.

Thus, the LS represents a continuous sample of the population of England and Wales, rather than a sample taken at one time point only. It now includes records for over 950,000 study members.

In addition to the census records, the individual LS records contain data for events such as deaths, births to sample mothers, emigrations and cancer registrations.

Census information is also included for all people living in the same household as the LS member. However, it is important to emphasise that the LS does not follow up household members in the same way from census to census.

Why was it set up?

The LS was planned in the late 1960s at a time of considerable concern about the adequacy of mortality data collected from death registrations, and about the lack of data on fertility patterns. For example, when a death is registered, only very limited socio-economic information can be collected about the dead person, some of which (e.g. occupation) may be either deficient or inconsistent with that collected while the person was alive. More reliable and more extensive statistics could be obtained by linking the death record with the earlier census return for that person.

Similarly, the information provided on birth certificates did not allow for studies of birth spacing. Although such data could be obtained from the General Household Survey (GHS), the total sample sizes were too small for detailed studies.

The 1971 Census was the first to include a question on date of birth (rather than age), and this, combined with advances in information technology, made the LS possible.

How do I access the LS?

The ONS grants access to the LS while maintaining the confidentiality of individuals in the data sample. To ensure confidentiality, the data can only be accessed in secure settings (Virtual Microdata Laboratories, or 'VMLs') at ONS offices in London, Newport (South Wales) and Titchfield (Hampshire) and only statistical abstracts or tabulations can be released to researchers. For this reason, researchers must apply to use the LS and two teams of support staff have been identified to assist and support researchers: academic and governmental researchers are supported by CeLSIUS and all other researchers by a team at ONS: longitudinalstudy [@] ons.gsi.gov.uk So, if you are staff or student in a UK higher education institution or governmental organisation, CeLSIUS staff can extract your data, run your analyses and release results to you. These results will be in the form of tabulations, models or aggregated datasets; individual-level data is never released.

Alternatively, you can go to ONS to analyse individual-level data directly. ONS or CeLSIUS staff will extract a dataset suitable for your purposes which you can analyse in the ONS office in Pimlico, London. It may be possible for users to visit ONS offices in Titchfield (Hampshire) or Newport (Wales) instead, but this is not guaranteed. Results which can be released from any ONS office will be subject to the same constraints as mentioned above - they may be tabulations, models or aggregated datasets but not individual-level data.

In both ways of working the process is iterative and fresh extracts can be made or fresh analyses carried out, as your research ideas develop.

How do I find out about the variables in the LS?

Most researchers begin by checking the questions asked in the census forms. The 2,800 plus variables available in the LS, up to and including the 2011 Census, are described in this online data dictionary. Additionally, CALLS-Hub have provided a dictionary that contains variable from across the UK LS'. 

The "metadata" (information about data) in the data dictionary include details of the range of each variable and relevant references to the LS Technical Volume (LS series no. 7) (PDF) and other publications on the source and quality of the data.

More information about the LS

Page last modified on 10 nov 16 15:01 by Joanne Tomlinson