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The ONS LS is stored at the Office for National Statistics and contains census and life events data (see table below), linked between five successive censuses beginning in 1971 and updated at the 1981, 1991, 2001 and 2011 Censuses. The sample is of people living in England and Wales who were born on one of four dates of birth, i.e. 4 out of 365 days of the year, so it makes up about 1% of the total population. Fresh LS members enter the study through birth and immigration and existing members leave through emigration or death, however their data is retained. The LS now includes records for over 1,100,000 individuals.
Why was the ONS LS set up?
The ONS 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 ONS LS possible.
What data does the ONS LS contain?
The ONS LS contains information on everyone usually living in the household, although only LS members are followed up from census to census.
Census data
| Age & sex | 1971 | 1981 | 1991 | 2001 | 2011 |
| Marital/civil partnership (2011 only) status | 1971 | 1981 | 1991 | 2001 | 2011 |
| Marriage and fertility history | 1971 | ||||
| Relationships in household | 1981 | 1991 | 2001 | 2011 | |
| Geographical data | 1971 | 1981 | 1991 | 2001 | 2011 |
| Type of accommodation & tenure | 1971 | 1981 | 1991 | 2001 | 2011 |
| Amenities of accommodation inc. no. of rooms, heating type (2011 only) | 1971 | 1981 | 1991 | 2001 | 2011 |
| Second address | 2011 | ||||
| Transport available to household members | 1971 | 1981 | 1991 | 2001 | 2011 |
| Country of birth | 1971 | 1981 | 1991 | 2001 | 2011 |
| Parents’ country of birth | 1971 | ||||
| Time since arrival and intended length of stay | 2011 | ||||
| Passports held | 2011 | ||||
| National identity | 2011 | ||||
| Ethnic group | 1991 | 2001 | 2011 | ||
| Main language and proficiency in English | 2011 | ||||
| Religion | 2001 | 2011 | |||
| Education level/qualifications | 1971 | 1981 | 1991 | 2001 | 2011 |
| Economic activity/employment/occupation/social class | 1971 | 1981 | 1991 | 2001 | 2011 |
| Migration and means of travel to work | 1971 | 1981 | 1991 | 2001 | 2011 |
| Caregiving | 2001 | 2011 | |||
| Self-rated health status | 2001 | 2011 | |||
| Limiting long-term illness or disability | 1991 | 2001 | 2011 | ||
| Visitors staying over on census night | 2001 | 2011 |
Life events data linked to ONS LS members' census records at any time
| Births (of Longitudinal Study members) |
| Immigration |
| Emigration |
| Maternity events to Longitudinal Study members (including live births, still births, infant deaths and birth weight) |
| Cancer registrations |
| Widow(er)hoods |
| Mortality (deaths of sample members), including full information from registration forms, such as cause of death |
What types of analysis can the ONS LS be used for?
- Prospective analysis of census and event data eg studies of associations between employment status and mortality, between economic status and cancer registrations, or between socio-economic factors and fertility; and survival analysis of mortality by area deprivation.
- Prospective analysis of successive census data eg analysis of patterns of retirement migration; studies of the effects of divorce and remarriage on housing tenure; or comparison of changes in education, employment and migration between different decades.
- Prospective analysis of successive event data eg studies of changes in birth spacing or associations between fertility and cancer survival.
- Cross-sectional analysis - this is especially useful for studies of ethnic or geographical factors.
- International comparisons - countries such as France, Denmark, Finland and the USA have similar programmes to the LS.
