Background variables are a set of mostly demographic variables, which have to be delivered as mandatory part of the national data sets. Unlike other surveys, countries in the ISSP are allowed to use ex-posto harmonisation. This means, the items’ measurement goals must be achieved in the end, but, countries are free to collect the crucial information via more or differently structured variables. This procedure is an artefact from the early years of the ISSP, where most ISSP surveys were “piggy-backed” on big national surveys, sharing the same set of background variables. Nowadays, this accounts only for minority of countries.
In the recent years the background variables underwent a stepwise and profound revision. A document called Background Variable Guidelines provides information on the measurement goals and coding instructions. The guideline document is accompanied by a background variable questionnaire. This questionnaire proposes precise wording and order of the ISSP BV questions, which should be followed by the participating countries if possible, or at least be seen as a reference document. In any case, the coding of the background variables has to be documented carefully. The completed documentation forms are listed on the GESIS ISSP module pages in the column “Background Variables”.
For ISSP modules up to ISSP 2009, the definition of ISSP background variables did not go beyond providing a coding frame on the respective data contents, and on delivering documentation on the exact derivation processes to meet this coding frame.
The first standard of ISSP background variables was agreed upon at the 2001 ISSP meeting in Umeå. All background variables were compulsory except 'nat_ETHN'.
Beginning with ISSP module 2010 'Environment', more elaborate guidelines on coding and collecting background variables were in effect.
This revised version of the ISSP background variables, plus accompanying guidelines, were agreed upon at the 2009 ISSP meeting in Vienna. All background variables were compulsory, including 'nat_ETHN'.
The background variable guidelines for the ISSP modules 2011 'Health and Health Care' and 2012 ‘Family and Changing Gender Roles’ were agreed upon at the 2010 ISSP meeting in Lisbon. All background variables are compulsory, including 'nat_ETHN'.
The background variable guidelines for the ISSP module 2013 'National Identity III', were agreed upon at the 2012 ISSP meeting in Cavtat. The main change are revised variables for the measurement of ethnicity. All background variables are compulsory.
The standard background variables to be used for ISSP module 2014 onwards differ from those of 2013 only in terms of the required occupational code scheme: ISCO-88 was replaced by ISCO-08. Along with information on the ISCO-08 structure, ILO provides spread sheets showing the correspondence between ISCO-88 and ISCO-08.