step,rule,n_before,n_after,n_removed,rationale
1,"keep one row per (iso3, year); drop exact-value duplicates",439,416,23,"duplicated country-years from two extractions (TUR as 'Turkey' and 'Turkiye'), identical values"
2,drop rows with empty life_expectancy,416,415,1,no recorded value; imputation not allowed
3,keep only countries with a recorded value in every year 2000-2022,415,345,70,"balanced-panel definition; excluded ['BGD', 'CHE', 'ETH', 'IND', 'NGA']"