1step,rule,n_before,n_after,n_removed,rationale21_drop_rating_2025,remove column rating_2025 (known only in 2025),2140,2140,0,Final-vintage rating built from realised defaults through 2022; not known at end of t (look-ahead leakage).32_drop_exact_duplicates,drop rows identical on all columns to an earlier row,2140,2100,40,Assembly error: duplicated firm-year records; keep one copy per firm-year.43_drop_unobserved_outcome,drop rows with empty default_next,2100,1800,300,Outcome year beyond data cut (end 2022); outcomes are not imputed.54_drop_missing_predictors,drop rows with any missing predictor,1800,1800,0,Complete-case for regressors.6