Dear all I run a regression with both years fixed effect and cluster standard error by firms, the result is below. I found the year fixed effect is so strange, why there are only two years. My data period is from 1990 to 2019. Can someone tell me what's wrong? I wrote down the code here.   proc surveyreg data=tmp1.dataset; class year; cluster permno; model future_accuracy = rw3_std varx vary varx*vary L_abnret AbnRet firm_age size lev BTM rw10_std busseg sdret earn year / solution; run;quit;   Also the degree of freedom here is strange, I have 20000 observations in my dataset but the degree of freedom here is only about 1000?   Anyone can help? Thanks in advance   ... View more