1step,rule,n_before,n_after,n_removed,rationale21,drop months s < 1992-03-01 (lags ip_growth_{s-2} and neworder_chg undefined before),417,415,2,task-specified training start32,drop months s with s+1 > last origin 2026-08-01 (target not available at origin),415,413,2,information-availability rule4