An analysis by ValuePenguin has concluded that Medford ranked in the top 10% most expensive cities in Massachusetts for car insurance. The company said it analyzed rates for seven different driver profiles from 35 insurers and 179 cities, and based on survey data, the average cost of car insurance in Massachusetts is $1,347. Annual premiums ranged from $1,015 to $2,350. Medford ranked as the 18th most expensive with an average cost of $1,664. Brockton was the most expensive while Nantucket was the least expensive. The full ranking is available on www.valuepenguin.com.