Hi all, I'm recently compling a data set that captures data about how car plants affect its surroundings. I have panel data and would like to create a new variable that captures whether if a car plant exist at certain year.

These are examples of my two data sets.

Economy data set:
zip year data
1 2018
1 2019
1 2020
2 2018
2 2019
2 2020
3 2018
3 2019
3 2020

Car plant data set:
zip built_date year
1 1998 2020
2 2016 2020
(I didn't have year 2020 before but added it so I can do merge 1:1 zip year)

What I have after the merge is something like this:
zip year data built_date
1 2018 .
1 2019 .
1 2020 1998
2 2018 .
2 2019 .
2 2020 2016
3 2018 .
3 2019 .
3 2020 .

I was hoping to create a new variable, if_Exist, that captures whether if the plant exist at year, andl perhaps also fill in the built_date for the empty cells. And I want to assign value 1 for plants with year >= built_date, and 0 if year < built_date.

However I tried various methods but the codes just won't run due to multiple syntax errors.

Can anyone please enlighten me how to get the codes that converts table 3 into the way I wanted? Filling the built_date part is now a must, but I really need the if_Exist varible to exist

Thank you!!