Question: Calculate the ratio in percentage between the average number of app users belonging to "80s Japanese comic" and "90s Japanese comic".
SQL: SELECT SUM(IIF(T1.category = '80s Japanese comic', 1, 0)) / COUNT(T1.label_id) AS J8 , SUM(IIF(T1.category = '90s Japanese comic', 1, 0)) / COUNT(T1.label_id) AS J9 FROM label_categories AS T1 INNER JOIN app_labels AS T2 ON T1.label_id = T2.label_id