GN:33298  Quarterly Labour Force Survey Household Datasets

Labour Force Survey (LFS) Reweighting Project 2007
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In 2007, the Office for National Statistics (ONS) undertook a reweighting
project, whereby LFS data were reweighted using population estimates for
2007-2008. As a result, reweighted editions of LFS back to 1992 were
deposited at UKDA during 2008. All applicable QLFS datasets have been
updated accordingly. 
Users should note that in the End User Licence (EUL) datasets:
* the single year of age variable (AGE), and 4-digit unit SOC for main
occupation, has been reinstated in the reweighted datasets.
* only calendar datasets have been reweighted to 2007-2008 figures.
The previous seasonal datasets are no longer updated or supported by
ONS and have been withdrawn from the UKDA catalogue accordingly.
For differences between the EUL and Special Licence (SL) QLFS datasets,
see below.

Weights
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After the 2007 reweighting exercise, a new household weighting variable
was introduced: phhwt07. Please note that the documentation may still refer to
weighting variables by their previous names until the next documentation update.

LFS Disclosure Risk Changes
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During 2008, at the request of the depositor, the variables age, dobm,
doby, nuts2, soc2kap, soc2kl, soc2kr and soc2ks were dropped from LFS
datasets from 2003 onwards, and a banded age variable (ageeul) created.
After the 2007 reweighting exercise, year of age (AGE) was reinstated,
though some datasets may still include AGEEUL as well.
These changes have been made to reduce the risk of disclosure, and will
be reflected in all new LFS datasets deposited at the UKDA.
Further details may be found in the document 'briefing_note_for_ukda_lfs.pdf'
contained in the documentation for affected LFS studies.
Special Licence Access datasets are unaffected.

LFS move from seasonal to calendar quarters
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In accordance with EU regulations, the LFS moved from seasonal (spring,
summer, autumn, winter) quarters to calendar quarters (January-March,
April-June, July-September, October-December) in 2006. Household datasets
are therefore released for each April-June and October-December quarter.
During the 2007 reweighting exercise, only calendar datasets were
reweighted to 2007-2008 figures. Seasonal datasets from 1997/2004 onwards
that have been replaced by calendar quarters have been withdrawn from the
UKDA catalogue at the request of the depositor, as they are no longer
supported. The remaining seasonal datasets (i.e. April-June household
quarters prior to 1997 and October-December household quarters prior to
2004) will stay weighted to Census 2001 population figures. ONS advise
that, because of the method of construction and the weighting factors
used in the datasets, comparison cannot be made between datasets of a
calendar and seasonal nature. Time series and longitudinal analysis
should only be conducted on datasets of the same type. Further information
on the seasonal to calendar quarter change and its impact on LFS data may
be found in the following online article:
Madouros, V. (2006) Impact of the switch from seasonal to calendar
quarters in the Labour Force Survey, London: ONS. Available from:
http://www.statistics.gov.uk/articles/labour_market_trends/CQ_article.pdf