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 death and emigration.

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.

More information about the LS

Page last modified on 26 feb 15 13:34 by Joanne Tomlinson