Hi everyone, I need some help in processing data for my phd research. I started with a dataset including firm-year observations from 2014-2019 but after the baseline regression I recognized that I also needed observations for year 2013, in order to implement the cross-sectional analysis. I downloaded the data for 2013 and now I need to append it to the previous dataset with observations from 2014-2019. The problem I have is that in the new download there are firms that were not present in the old file (with data from 2014-19) because Orbis has updated its data. How can I delete those firms that have a single year observation (2013) and keep only firms that match within the files?

At the moment I launched the append command and after I sorted by country, company name and year. Then how to drop unmatched firms?

Thanks a lot for the help!