Database schema:

CREATE TABLE playstore (
	"App" TEXT -- example: ['Photo Editor & Candy Camera & Grid & ScrapBook', 'Coloring book moana'],
	"Category" TEXT -- example: ['AUTO_AND_VEHICLES', 'ART_AND_DESIGN'],
	"Rating" REAL -- example: ['3.9', '4.1'],
	"Reviews" INTEGER -- example: ['159', '967'],
	"Size" TEXT -- example: ['19M', '14M'],
	"Installs" TEXT -- example: ['500,000+', '10,000+'],
	"Type" TEXT -- example: ['Paid', 'Free'],
	"Price" TEXT -- example: ['0', '$4.99'],
	"Content Rating" TEXT -- example: ['Everyone', 'Teen'],
	"Genres" TEXT -- example: ['Art & Design;Pretend Play', 'Art & Design']
)


CREATE TABLE user_reviews (
	"App" TEXT -- example: ['104 找工作 - 找工作 找打工 找兼職 履歷健檢 履歷診療室', '10 Best Foods for You'],
	"Translated_Review" TEXT -- example: ["I like eat delicious food. That's I'm cooking food", 'This help eating healthy exercise regular basis'],
	"Sentiment" TEXT -- example: ['nan', 'Positive'],
	"Sentiment_Polarity" TEXT -- example: ['1.0', '0.25'],
	"Sentiment_Subjectivity" TEXT -- example: ['0.5333333333333333', '0.28846153846153844'],
	CONSTRAINT fk_user_reviews_playstore FOREIGN KEY("App") REFERENCES playstore ("App")
)

Question: What is the percentage for free application with a rating 4.5 and above have not been updated since 2018?
Evidence: 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;

SQL:
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