st: state the same for multiple observations?

["Ms. Marilyn Ibarra" <ibarra@uga.edu>]

Anyone have an idea of how I can do the following: 

The data looks something like this: 

us_id       state
1               CA
1               CA
2               VA
3               PA
3               TX

I need to know if when a us_id has multiple observations is the state the same for each observation in that us_id.  If the state is different for a given us_id I need to be able to easily identify those cases. 

Thanks in advance,
Marilyn. 
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