Database: soccer_2016
Question: Among the players, what percentage are both captain and keeper?
SQL: SELECT CAST(SUM(CASE WHEN T2.Role_Desc = 'CaptainKeeper' THEN 1 ELSE 0 END) AS REAL) * 100 / TOTAL(T1.Player_Id) FROM Player_Match AS T1 INNER JOIN Rolee AS T2 ON T1.Role_Id = T2.Role_Id