1step,rule,n_before,n_after,n_removed,rationale21,keep quarters 1960Q1-2019Q4 (union of GDPC1/UNRATE quarterly index),319,240,79,information rule: regression sample; pre-1960 used only as lag for 1960Q1 difference; post-2019 excluded32,drop quarters with missing du or g,240,240,0,no missing values expected inside the window4