What is the percentage for free application with a rating 4.5 and above have not been updated since 2018?
paid refers to Type = 'Paid'; application refers to App; Rating>4.5; Last Updated>'2018; percentage = DIVIDE(SUM(Genres = 'Mature 17+' and Rating>4.5 and substr("Last Updated",-4,4)>'2018' )), (COUNT(App)) as percent;
SELECT CAST(SUM(CASE WHEN SUBSTR('Last Updated', -4) > '2018' THEN 1 ELSE 0 END) AS REAL) * 100 / COUNT(App) PER FROM playstore WHERE Type = 'Free' AND Rating >= 4.5
database name:db_id app_store
googleplaystore table googleplaystore Cols: App dtype text, Category dtype text, Rating dtype real, Reviews dtype integer, Size dtype text, Installs dtype text, Type dtype text, Price dtype text, Content Rating dtype text, Genres dtype text, 
googleplaystore_user_reviews table googleplaystore_user_reviews Cols: App dtype text, Translated_Review dtype text, Sentiment dtype text, Sentiment Polarity dtype text, Sentiment Subjectivity dtype text, 
