step,rule,n_before,n_after,n_removed,rationale
0_read,read all data rows of data/firms.csv,445,445,0,starting row count
1_dedup_exact,drop rows identical on all columns to an earlier row (keep first),445,400,45,assembly error: same firm appended more than once from overlapping extracts
2_unit_convert,convert revenue to millions USD (USD_thousands / 1000; USD_millions unchanged),400,400,0,"mixed units across extracts; 60 distinct firms recorded in USD_thousands (transformation, no rows removed)"
3_drop_missing_revenue,drop firms with empty revenue: F0048;F0121;F0129;F0269;F0348;F0399,400,394,6,revenue unknown; cannot contribute to revenue aggregates (employees still used for mean_employees)