step,rule,n_before,n_after,n_removed,rationale
1,drop region == 'Aggregates',2349,1953,396,analysis population is countries/economies only (TASK info rule)
2,keep year == 2023,1953,217,1736,latest year 2015-2023 with both indicators for >=150 countries/economies
3,drop rows with missing gdp_pc_ppp or life_expectancy,217,197,20,no imputation (TASK info rule)