I've enlisted policy as a binary variable which I need to take 1 year forward. Like in my data for county 1003 the policy takes value 1 at year 2021. But, I need to create a new variable where the policy will take the value 1 for county 1003 at year =2022. Same goes for each observation. I have a repeated cross section dataset.

Can anyone kindly take me how I can execute it? Here is the sample data for your convenience.

Code:
* Example generated by -dataex-. For more info, type help dataex
clear
input float policy double county int year
0 1003 2002
1 1003 2021
0 2012 2002
0 1003 2002
1 1004 2015
0 1004 2004
0 1013 2002
1 1013 2018
1 10003 2004
0 12003 2009
0 10003 2000
1 12003 2014
0 10101 2021
1 12003 2014
end