Derivation
variable: mardate (table[s]: all_spouse_pairs_full [derived table])
variable: rmardate (table[s]: all_spouse_pairs_full [derived table])
variable: rsepdate (table[s]: all_spouse_pairs_full [derived table])
the mode of the reported marriage dates is taken first (this is the date estimated from the marriage start year reported by either partner). It is updated to the earliest co-residency date if this is earlier, or in the same year but different date (as the reported values are all estimated as 15 April).