Dear professors, fellow PhD candidates, and members of this forum, I just subscribed to the forum however, your questions and answers helped me out through my academic years.

Currently I am doing research for my PhD thesis. I am using an unbalanced data which includes firm level dataset, their industries their years, etc.

I am using two different surveys from 2009 to 2019 (11 years in total). My question is, recently the statistical agency added the regional codes in their 2019 dataset which did not exist in the previous 10 years datasets. We have firm IDs but I do not know how to change the empty cells from earlier years' data. How can I match previous years firm data to their regions accordingly?

I have been using many dummies so far and I am very used to create dummies however for this one, I am struggling.

Thank you for your understanding, I hope I was able to explain the situation and it was clear.

Sincerely from Istanbul, Turkey.