1step,rule,n_before,n_after,n_removed,rationale2merge_unrate,"keep GDPC1 quarters with a complete (3-month, non-missing) UNRATE quarterly average",319,314,5,"UNRATE (945 monthly rows) averaged to quarters; 1947 has no UNRATE, 2025Q4 lacks Oct-2025 value"3window,keep 1959Q4-2019Q4 (1959Q4 only for differencing),314,241,73,"information rule: fixed sample window, no extension"4differencing,drop 1959Q4 (levels used only to form 1960Q1 differences),241,240,1,first difference unavailable for base quarter5