https://stats.idre.ucla.edu/stata/faq/how-can-i-merge-multiple-files-in-stata/
https://www.eastonbh.ac.nz/2002/11/household_equivalence_scales/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3114612/
https://www.eastonbh.ac.nz/2002/11/household_equivalence_scales/