Calculate the percentage of famous_legislatorss.
percentage = MULTIPLY(DIVIDE(SUM(wikipedia_id is not null), (bioguide_id)), 100.0); famous legislators refers to wikipedia_id is not null;
SELECT CAST(SUM(CASE WHEN wikipedia_id IS NOT NULL THEN 1 ELSE 0 END) AS REAL) * 100 / COUNT(bioguide_id) FROM historical