Deat Statalist,

I have a set of variables from 2010-2012, I want to compare which companies are new to the dataset (i.e., not in the data in 2010, but in the data in 2011; not in the data in 2011, but in the data in 2012).

Just give an example:

Symbol Year
A 2010
B 2010
C 2010
D 2010
E 2010
A 2011
C 2011
D 2011
F 2011
G 2011
B 2012
C 2012
G 2012
H 2012
I 2012

Thanks a lot in advance!