What is the ratio of author with affiliation and without affiliation?
with affiliation refers to Affiliation is not Null; without affiliation refers to Affiliation IS NULL; Ration = Count(Id(Affiliation is NOT NULL)) : Count (Id (Affiliation IS NULL))
SELECT CAST(SUM(CASE WHEN Affiliation IS NULL THEN 1 ELSE 0 END) AS REAL) / COUNT(*) FROM Author