Calculate the percentage of voice actors whose main character in the movie is in the Drama genre.
DIVIDE(COUNT(voice-actor where genre = 'Drama'), COUNT(voice-actor)) as percentage;
SELECT CAST(COUNT(CASE WHEN T1.genre = 'Drama' THEN T3.`voice-actor` ELSE NULL END) AS REAL) * 100 / COUNT(T3.`voice-actor`) FROM movies_total_gross AS T1 INNER JOIN characters AS T2 ON T1.movie_title = T2.movie_title INNER JOIN `voice-actors` AS T3 ON T3.movie = T1.movie_title