Derivation
variable: stillmardate (table[s]: all_spouse_pairs_full [derived table])
<after all the summary dates are finalised the latest date either of the partners reported being married to the other partner that is on or before sepdate or stillmardate is taken:>
egen end=rowmax(stillmardate sepdate)
bys wife husband: egen temp2=max(stillmardateO) if stillmardateO~=. & stillmardateO<=end
bys wife husband: egen lstmarrepdate=max(temp2)