What percentage of restaurants are from the Bay Area?
Bay Area refers to region = 'bay area'; percentage = divide(count(id_restaurant where region = 'bay area'), count(id_restaurant)) * 100%
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