CREATE TABLE table_name_54 (year VARCHAR2, hmos VARCHAR2, pos_plans VARCHAR2)

How many years have HMOs been 27% and POS plans 18%?
SELECT COUNT(year) FROM table_name_54 WHERE hmos = "27%" AND pos_plans = "18%"
SELECT COUNT("year") FROM "table_name_54" WHERE "18%" = "pos_plans" AND "27%" = "hmos"