Dealing with unbalanced dataset

This is my first work in Stata. I have to deal with an unbalanced but well-shaped dataset the (GGDC 10 sector database). It contains each observation for every country but with different starting date. I don't want to reduce the analysis to a common sample. I don't know from where I should start.

I would like to do a regression similar to the one done by Rodrik in this paper: http://drodrik.scholar.harvard.edu/f...f?m=1447439197 (tab 2 in the appendix).

Thanks in advance