Individual Tracking File
Person core information and respondent status for each year in long format. It contains one record for each individual and year a person has been a member of a respondent household. It is keyed on PID, the Cross-Wave Person Identifier, and SYEAR, the survey year identifier. It contains the Household ID, and never changing individual characteristics, individual weights, as well as the response status, for that individual at each wave, see http://www.diw.de/documents/dokumentenarchiv/17/diw_01.c.432038.de/diw_ssp0150_ppfad.pdf.