National average prices for retail regular unleaded gasoline continued their decline this week to $2.27 and have fallen for 21 consecutive days, reports AAA.

The national average price has fallen four cents from a week ago and five cents from a month ago, but is 47 cents higher than a year ago. Increased crude oil production and lower driving demand has "kept downward pressure on the national average price at the pump," according to AAA.

Federal data remains closely aligned to AAA reporting. Gasoline prices as tracked by the U.S. Energy Information Administration fell three cents to $2.296. The price is 47.4 cents higher than a year ago.

The nation’s top five most expensive markets include Hawaii ($3.07), California ($2.80), Alaska ($2.74), Washington ($2.73), and Pennsylvania ($2.57).

The top five markets with the most dramatic monthly decreases in gas prices include Ohio (33 cents), Indiana (31 cents), Michigan (18 cents), Illinois (18 cents), and Kentucky (17 cents).

Meanwhile, the average price of diesel fell seven-tenths of a cent to $2.562. Diesel is now 53.1 cents higher than a year ago.