Panel data regression: Robust standard errors
问题 my problem is this: I get NA where I should get some values in the computation of robust standard errors. I am trying to do a fixed effect panel regression with cluster-robust standard errors. For this, I follow Arai (2011) who on p. 3 follows Stock/ Watson (2006) (later published in Econometrica, for those who have access). I would like to correct the degrees of freedom by (M/(M-1)*(N-1)/(N-K) against downward bias as my number of clusters is finite and I have unbalanced data. Similar