Eligibility and Follow-up¶
As mentioned, the SOEP’s goal is to be representative of the residential population of Germany. All household members 16 and older are eligible for a personal interview, starting with the youth questionnaire at that age, followed by “regular” person questionnaires thereafter. As years go by, the children of the first wave reach age-eligibility and become panel members. If they move out and form their own families, they and their new families are still part of the survey. “New” persons become part of the SOEP population due to birth or residential mobility. In case a person enters a SOEP household after the initial wave, this person is asked to fill out the regular person questionnaire if age-eligible, or will be asked to participate once old enough. Thus in the absence of panel attrition the SOEP would be a self-sustaining survey.
The concept of how to follow the respondents and sample members over time is important for the representativeness of the study. The basic principle for follow-up in the SOEP is that all persons participating in a wave of any subsample are to be surveyed in the following years as long as they stay within the boundaries of Germany. This rule also extends to respondents who entered a SOEP-household after the first wave due to residential mobility or birth. If there is a “split-off”, i.e. people move out of the household they were last interviewed in, the members of the new household receive a new household identifier. The table conceptualizes how new sample members and households are realized in the SOEP. The figure shows that as a result of the follow-up concept, up to , several thousand “new” households became part of the SOEP population.
Persons or households who could not be interviewed in a given year are termed “temporary drop-outs”. These are followed until there are two consecutive waves of missing interviews for all household members or a final refusal of the complete household. In the case of a cooperation after a temporary drop-out, the respondent is asked to fill out an additional short questionnaire on central information on employment and demographics during the year of absence.
|Existing Households||New Households|
|Existing Persons||classic case: without change of adress entire household moves||Move-out|
|New Persons||Birth Move-In||Move-In or birth into move-out household|
Changes to the Sample: Old and new household in the SOEP