Derivation
variable: weight (table[s]: arkk_arkq, arkl_arkq, phdk_hsbc, phdl_hsbc)
variable: weightf (table[s]: kduk_kduq, kdul_kduq, phdk_phdq, phdl_phdq)
variable: weights (table[s]: kduk_kduq, kdul_kduq, phdk_phdq, phdl_phdq)
variable: weight_kg_hw (table[s]: NUTdata_KAR, NUTdata_LLW)
variable: a_wt (table[s]: gap_combined)
<KDU data:>
egen weight=rowmean(weightf weights)
<PHD data:>
egen weight2=rowmean(weightf weights weight)
drop weight
rename weight2 weight