step,rule,n_before,n_after,n_removed,rationale
1_dedupe,"drop duplicate (iso3, year) rows; keep one per country-year",439,416,23,each country contributes at most one observation per year; duplicates had identical values
2_drop_missing,drop rows with empty life_expectancy,416,415,1,no imputation allowed; a country-year without a recorded value is missing
3_year_range,keep years 2000-2022,415,415,0,study window
4_balanced_panel,keep countries with a recorded value in every year 2000-2022,415,345,70,"balanced-panel estimand; excluded countries: BGD, CHE, ETH, IND, NGA"