Hello, I need some help

I have large unbalance panel data and I need to drop the Person ID (PID) if its next year data is missing. See the sample:

PID Year Explanatory variable
1 2009 12
1 2010 12
1 2011 7
1 2012 8
1 2013 14
2 2009 12
3 2009 45
3 2010 56
3 2011 34
3 2012 23
4 2009 212
5 2009 12
5 2010 34

So at time 1 which is 2009, I am considering data of Persons then its impact will be on the Dependent Variable next year data time 2. So, if PID is missing in next year these observations are useless for me. Example PID: 2 and 4 above. How I can drop them I cannot do it manually its huge data base.