1step,rule,n_before,n_after,n_removed,rationale21_dedupe,"drop duplicate (iso3, year) rows with identical values",439,416,23,each country contributes at most one observation per year (TASK rule); duplicates are assembly artefacts32_year_window,keep years 2000-2022,416,416,0,estimand window43_drop_missing,drop rows with empty life_expectancy,416,415,1,missing values are not imputed (TASK rule)54_balanced,keep countries with a recorded value in every year 2000-2022,415,345,70,"balanced-panel estimand; excluded incomplete countries ['BGD', 'CHE', 'ETH', 'IND', 'NGA']"6