Derivation
variable: sex (table[s]: gen_identity_clear [derived table])
<on all_spouse_pairs_clean_summarised:>
expand 2, gen(exp1)
gen sex=0 if exp1==1
replace sex=1 if exp1==0
<on all_marstatus_reports:>
merge m:1 ident using ${newstata}\gen_identity_clean, keep(master match) keepusing(sex) nogen