1step,rule,n_before,n_after,n_removed,rationale2G1,keep GDPC1 quarters in 1959Q4-2019Q4,319,241,78,window rule: outside 1960Q1-2019Q4 only 1959Q4 levels are used3M1,inner-join with quarters having 3 non-missing UNRATE months,241,241,0,u_t requires complete quarter (none missing in window)4Q1,drop 1959Q4 (levels-only quarter used for first differences),241,240,1,differencing5