1step,rule,n_before,n_after,n_removed,rationale22025-12-31:sample_start,drop quarters before 1985-01-01 (model only),314,163,151,post-Great-Moderation estimation sample for AR(1)32025-12-31:pandemic,set 2020-04-01 and 2020-07-01 to missing (model only),163,161,2,extreme pandemic swings would dominate OLS AR coefficient4