I am investigating how certain factors affect hedging. For this I used xttobit. Now my exogenous variable "HEDGING" consists of a total of 450 observations and 50 of them are empty. I thought if I set xttobit's left censoring to zero, it works. But that doesn't work, stata says I have over 200 left censored observations (he also takes all zeros with him). How can I set the censoring so that it doesn't look at the empty lines?

My idea was to enter a -2 anywhere where it is empty and then enter -1 for the link censoring. This works, but I think the estimate is biased.

I hope you can help me,

many greetings,
Patrick