Table: health_insurance_plans
Columns: year
conventional_plans
hmos
ppos
pos_plans

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

Question: Which conventional plan has a POS of 13%?
SQL: SELECT "conventional_plans" FROM health_insurance_plans WHERE "pos_plans" = '13%'

Question: How many years have a conventional plan of 7%?
SQL: SELECT SUM("year") FROM health_insurance_plans WHERE "conventional_plans" = '7%'

Question: Which conventional plan has a POS plan of 21%?
SQL: SELECT "conventional_plans" FROM health_insurance_plans WHERE "pos_plans" = '21%'

Question: Which HMO has a conventional plan of 3% in 2005?
SQL: SELECT "hmos" FROM health_insurance_plans WHERE "conventional_plans" = '3%' AND "year" = 2005