I'm sorry, I was unclear with my question. I restate it, dropping the first part.
I start with a panel data set consisting of "x" firm-year observations.
Question 1: I need to divide firms evenly into three groups according to their value in each year, getting these groups: firms residing in the low-, in the middle- and in the high-var1 group. I underline that the calculation should be done for each year, and that each year I have "x/3" observations for each group. I really don't know how realize this result. Any illustrative example would be of help. Thank you.
Question2: if the variable I want to split is incomplete in my initial data set (i.e. "." for some firm-year data), should I balance my data set before the sample splitting? Thanks for any suggestion!
D.
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