Write SQL query to solve given problem: What is the ratio of the number of app users that belong to the Securities category to the number of app users that belong to the Finance category?. Keep the solution inside sql tag ```sql [SQL-Query] ```
SELECT SUM(IIF(T2.category = 'Securities', 1, 0)) / SUM(IIF(T2.category = 'Finance', 1, 0)) AS per FROM app_labels AS T1 INNER JOIN label_categories AS T2 ON T1.label_id = T2.label_id