用多期DID,**2014年政策
gen Open1=0
replace Open1=1 if fabsorb == 2014
gen Post1=0
replace Post1=1 if year >= 2014
gen a1 = Open1 * Post1
**2016年政策
gen Open2=0
replace Open2=1 if fabsorb == 2016
gen Post2=0
replace Post2=1 if year >= 2016
gen a2 = Open2 * Post2
gen Open×Post=a1 + a2
gen Open = Open1 + Open2
类似于这样