Like many medical studies, the Berlin Aging Study II (BASE-II) is based on a non-random "convenience sample" of self-recruited participants. To study processes of selectivity in BASE-II, we used an identical questionnaire to compare BASE-II with a large, representative reference study, the...

In this paper we discuss the rationale for tracing non-original sample members (Non-OSMs) in household panel studies, and in particular in SOEP, and the implications for weighting. We present results on the incidence, survival rates, and thus the relevance of Non-OSMs in the SOEP.