step,rule,n_before,n_after,n_removed,rationale
1,read data/firms.csv,445,445,0,All data rows read (header excluded).
2,drop exact duplicate rows,445,400,45,Rows identical in every column are assembly duplicates of the same firm; keep first occurrence.
3,convert revenue to millions USD,400,400,0,Rows with unit USD_thousands divided by 1000; USD_millions unchanged. No rows removed.
4,exclude firms with unknown revenue,400,394,6,Empty revenue cell; cannot contribute to revenue aggregates. Firms: F0048;F0121;F0129;F0269;F0348;F0399