What percent of the non volcanic islands in the Lesser Antilles group of islands have an area of no more than 300 square kilometers?
Percent = [count(non volcanic islands Lesser Antilles area 300 or less) / count(non volcanic islands Lesser Antilles)] * 100%
SELECT SUM(CASE WHEN Area <= 300 THEN 1 ELSE 0 END) * 100 / COUNT(*) FROM island WHERE Islands = 'Lesser Antilles' AND (Type != 'volcanic' OR Type IS NULL)