04-01-2018 11:37 AM
Hello. I have a panel with isin codes as company IDs and years from 2009 to 2017.The coverage for the companies are not proportional. Some have data only for one year and some have for all years. Now I want to keep only the companies that have data for the years 2013 to 2016. How can I code for this? And is it possible to create a new variable called firm-year that combines the isin codes and the years of coverage?