Hello!

I want to perform the Kolmogorov –Smirnov test to a panel database given that it is a frequently employed method within the literature. I have to simple questions:
1) My panel database includes from the whole population 70% of firms with more than 200 workers while less than 5% of firms with less than 200 workers. Can I use this database?
2) I want to check if exporting firms are more productive than non-exporting firms. However, firm j can be non-exporters in year t, become exporter in year t+1, and become non-exporters in year t+2. Can I compare the productivity between the group of firms that are exporters vs non-exporters, if firms switch status over time? If so, do I need any specific command for the K-S test?

Thank you very much for your time.