Write SQL query to solve given problem: What percentage of restaurants are from the Bay Area?. Keep the solution inside sql tag ```sql [SQL-Query] ```
SELECT CAST(SUM(IIF(T1.region = 'bay area', 1, 0)) AS REAL) * 100 / COUNT(T2.id_restaurant) FROM geographic AS T1 INNER JOIN location AS T2 ON T1.city = T2.city