(LOS ANGELES) — The entire country is now paying more for regular unleaded gas than this time last year, according to the Energy Department.In the past week alone, the price per gallon rose 5 cents nationally to $2.75. But in California, the hike has been even greater.Prices at the pump in the Golden State have jumped almost 20 cents in the past week. Regular unleaded gas in many areas is even nearing $4 a gallon for the first time since 2014.Economist Severin Borenstein at UC Berkeley says refinery problems are to blame for in the increase.“California has a formulation that is not used anywhere else in the world,” Borenstein explains. “It’s cleaner burning than anybody else and it does help keep our air clean. But it does mean that we pay more.”Copyright © 2019, ABC Radio. All rights reserved.