step,rule,n_before,n_after,n_removed,rationale
1,drop exact duplicate rows (all columns identical),445,400,45,file assembled from several extracts; identical repeated rows are assembly errors
2,convert revenue to millions USD (USD_thousands /1000; USD_millions unchanged),400,400,0,mixed currency units across extracts; outputs must be in millions USD
3,drop firms with empty revenue: F0048;F0121;F0129;F0269;F0348;F0399,400,394,6,revenue unknown; cannot contribute to revenue aggregates (still counted in mean_employees)