Question: What is the percentage of male clients complaining about their credit cards?
SQL: SELECT CAST(SUM(CASE WHEN T1.sex = 'Male' THEN 1 ELSE 0 END) AS REAL) * 100 / COUNT(T1.sex) FROM client AS T1 INNER JOIN events AS T2 ON T1.client_id = T2.Client_ID WHERE T2.Product = 'Credit card'