Hi stata forum,

I would like to delete the whole firm if revenue is missing for more than or equal 30% of the rows within firm.
Any suggestions?

before:
firm_id year Revenue
1 1 0
1 2 0
1 3 0
1 4 1000000
1 5 0
1 6 1500000
2 1 20000
2 2 100000
2 3 0
2 4 1000000
2 5 10000000
2 6 1500000

After:
firm_id year Revenue
2 1 20000
2 2 100000
2 3 0
2 4 1000000
2 5 10000000
2 6 1500000