What is the ratio of males and females among historical legislators?
male refers to gender_bio = 'M'; female refers to gender_bio = 'F'; calculation = DIVIDE(COUNT(gender_bio = 'M' THEN bioguide_id), COUNT(gender_bio = 'F' THEN bioguide_id))
SELECT CAST(SUM(CASE WHEN gender_bio = 'M' THEN 1 ELSE 0 END) AS REAL) / SUM(CASE WHEN gender_bio = 'F' THEN 1 ELSE 0 END) FROM historical