Understanding Society User Support

Dear Sir or Madam,

I have a question regarding the variables social class of first job (j1gold) and parental social class of origin (pagold). Are these the only variables to look at?
These variables both have a lot of missing values in the first wave (wave a for pagold; wave h for pagold). I was wondering of the reason for so many inapplicable, missing cases? In the case of j1gold that is far more than people who say they never had a job.
My hunch is that there must somewhere be another variable capturing these things (and perhaps j1gold and pagold are just asked for the people who are new in the panel in that wave? Could you perhaps help me in figuring out how I best get to the information on social class of first job and parental social class of origin, for the whole sample?

Thank you.
Best wishes,
Leen