import excel using data.xlsx,firstrow sheet("1995")
gen year=1995
save data1995,replace
import excel using data.xlsx,firstrow sheet("2000")
gen year=2000
save data2000,replace
import excel using data.xlsx,firstrow sheet("2005")
gen year=2005
save data2005,replace
use data1995,clear
append using data2000
append using data2005
save data,replace