{"years_range": [1981, 2005], "num_years": 25, "macro_shape": [25, 4], "nIssuers_shape": [25, 7], "nNewIssuers_shape": [25, 7], "trans_prob_shape": [25, 6, 9], "trans_row_sum_min": 0.9998, "trans_row_sum_max": 1.0002, "assumptions": ["AAA issuer bucket dropped to align with 6x9 transition matrices", "First row of each TransMat sheet treated as header and removed", "Destination state ordering assumed as [AAA, AA, A, BBB, BB, B, CCC, D, NR]", "AAA destination state excluded from IG/SG aggregation and probabilities renormalized"]}