Some dasets contain variables with the suffix “_is”. What does this mean?

Over the years, SOEP-IS has modified some questions from SOEP-Core, resulting in new versions of variables. In some cases, additional variables were also necessary in order to record specific information. If variables are available exclusively in SOEP-IS but do not originate from innovative modules, these variables are marked with the suffix “_is”. These variables can only be compared with other variables to a limited extent and are therefore separated. However, it may be necessary to access them for some information (e.g. plb0568_is).