Understanding Society User Support

Hi Megan,
the variables mnpid and fnpid refer to the natural mother/father’s PIDP in the UKHLS. That PIDP may change over time as a result of new information coming through in a particular wave, for example, as the parent realises we make a distinction between natural and adoptive parents and they are not in fact a natural parent. Another route is that the parent’s gender may be incorrectly recorded in the study data base in a particular wave (resulting in mother and father switch) or there may be same-sex parents but only one can be recorded in the gender-specific pointer. Another route for inconsistencies across studies is that the information is asked differently: in the BHPS, household relationships are inferred from the relationship to the head of household; in the UKHLS relationships of each person are asked directly.

There will not be many cases with cross-wave inconsistencies. But (like all data errors/inconsistencies) these should be investigated; if you have a better idea about why the inconsistencies occur you can decide for yourself how to deal with these cases in your specific analysis.

Note that the UKHLS provides both the PID and the PIDP for respondents who already participated in BHPS W1-18. However, BHPS sample members who did not already appear in BHPS W1-18 will have their PID in the UKHLS set to -8 "inapplicable" (like all members of the new UKHLS samples). Therefore, for those pairs who occur in the BHPS W1-18 you could rely solely on the PID but for all others you have to use PIDP (or generate a new unique ID that works across studies). Once you have created an ID that works across studies and cleaned the parent-pointers, linkage is straightforward (as you describe).

Hope this helps, best wishes,
Gundi