Friday, 7 October 2011

Changes to Quarterly Labour Force Survey ID variables

End User License data:

The new release of the QLFS data files for January-March 2011 contain new ID variables/numbers which are designed to improve the confidentiality of respondents, which has some impact on the way in which the data can be used. The new identifiers are:

CASENOP - ‘Case Identifier - pseudoanonymised’
HSERIALP - ‘Number uniquely identifies a household - pseudoanonymised’

These ID numbers are designed to permit users to link household members together, but not to link across waves to create their own longitudinal datasets (users who wish to do this should use the LFS longitudinal files). The household identifier (hserialp) is an identifier which starts at 1 and simply counts up. Common values of this variable across waves no longer indicate that the case is from the same household. The numbers are no longer based on administrative data, and many of these administrative variables have been removed for reasons of confidentiality. Accordingly, previous guidance on how to generate person and household identifiers from these administrative variables has been superceded. It should still be possible to combine datasets in order to increase sample size as variables indicating which wave of the survey the respondent is in and when the respondent entered are still present. However, it is no longer possible to check that individual cases have not been duplicated as a result of failures in the merge process. It is still possible to use the data to identify household membership using the hserialp variable. However, users are reminded that when undertaking household analysis the most suitable data for household level analysis or analyses which involve household context are the household LFS files. All future QLFS datasets will contain these two new identifier variables. A variable called QUOTAP is also available which is the ‘stint number where interview took place - pseudoanonymised’

QLFS April-June 2009-October-December 2010 - these data files contain a new ID number (IDREF) which preceded the new ID variables for the January-March 2011 dataset (see above). IDREF was designed to improve the confidentiality of respondents, which has some impact on the way in which the data can be used. IDREF does not allow linkage between quarters (nor do Casenop and HserialP – see notes above). Please note that there is no household identifier on these datasets.

QLFS 2001-2009 - there are no changes to the ID variables in these QLFS datafiles – they should contain the original QLFS identifier variables (caseno, add, quota etc).

Special Licence (SL) data:

All Special Licence QLFS datasets should still contain the original ID variables (caseno, add, quota etc) so they are not affected by the above changes.

No comments: