Hello everyone,

I am new to Stata and as a part of my bachelor thesis, I have to do a fixed effect regression based on three waves of household panel survey. I initially have three separate cross section data of the survey each year and I appended all three waves into one data set. However, for my regression analysis I only want to observe individuals that respond to all three surveys. Four variables are of interest here: persnr (the personal identification number), 1985, 1990 and 1992 (0 if the respondent does not respond to the questioner in that year, 1 if he or she does).
Which command or function allows me to drop respondents that do not answer all three of the questionnaires?
I would appreciate any help or advice that you can give me about this matter. Thank you very much.

Regards,
Daisy