1step,rule,n_before,n_after,n_removed,rationale21_dedup,"drop duplicate (iso3, year) rows (identical values)",439,416,23,each country contributes at most one observation per year; duplicates came from assembling two extractions32_missing_value,drop rows with empty life_expectancy,416,415,1,an empty cell means no recorded value; no imputation allowed43_balanced_panel,keep countries with a recorded value in every year 2000-2022,415,345,70,"balanced-panel estimand; incomplete countries: ['BGD', 'CHE', 'ETH', 'IND', 'NGA']"5