Question: What is the percentage of horror film titles in English film titles?
SQL: SELECT CAST(SUM(IIF(T3.name = 'Horror', 1, 0)) AS REAL) * 100 / COUNT(T1.film_id) FROM film_category AS T1 INNER JOIN film AS T2 ON T1.film_id = T2.film_id INNER JOIN category AS T3 ON T1.category_id = T3.category_id INNER JOIN language AS T4 ON T2.language_id = T4.language_id WHERE T4.name = 'English'