Balanced panel for differenced GMM

[Raphael George]

I am trying to create a balanced panel of districts to run a differenced GMM.
How do I make sure that all the districts are there for all years? And delete the districts that are missing in some years?
Is it necessary to have a balanced panel for differenced GMM?

[Andrew Musau]

Is it necessary to have a balanced panel for differenced GMM?

No, the available estimators work well with unbalanced panels. You risk biasing your results by dropping observations, so I would not recommend doing it. But for future reference, see

ssc describe xtbalance2

for creating a balanced panel out of an unbalanced panel.