xtset id year
gen distance = year - policy_year
replace distance = -4 if distance < -4
replace distance = 2 if distance  > 2

forvalues i = 4(-1)1{
gen pre_`i' = (distance == -`i' & treat == 1)
}
gen current = (distance == 0 & treat== 1)
forvalues j = 1(1)2{
gen  time_`j' = (distance == `j' & treat == 1)
}

xtreg happiness did  pre_* current time_* $person $family $social i.year i.diqu1, fe vce(cluster id)

发在楼下了 能麻烦您看一下嘛~

请问楼主解决omitted的问题了吗？我也遇到这个问题呜呜