st: Obs per Group for xtregar

[Lisa McGuff <lmcguff@econone.com>]

I’m using xtregar and having trouble identifying which records Stata is using and which it is dropping.  The max obs per group is one less than the actual maximum number of observations in my data, which makes sense to me.  The minimum however is listed as 1 and I don’t understand this.  The least number of observations in a group of my raw data is 34.  I have no missing values.  My panel is unbalanced, with gaps throughout the data if that matters.  When does Stata drop observations?

 

Thanks,