The trend of falling gasoline prices continues and now 13 states can fill up for under $2 a gallon, according to CNN.

The national average price of gasoline 12.5 cents cheaper for the week ending Dec. 15. Figures from AAA's Daily Fuel Gauge Report show the average is currently $2.55 per gallon.

The boom in North American oil production in recent years has given the continent the lowest price for crude oil anywhere in the world, says Tom Kloza, chief oil analyst for the Oil Price Information Service. 

The price is 68.5 cents cheaper than it was a year ago. Once again the price of a gallon of unleaded had its steepest decline in the Midwest of 16.9 cents to $2.41. The average price that had the least amount of decline is on the East Coast in the lower Atlantic region. This area has an average gas price of $2.53.

The average price of diesel also dropped 9 cents to $3.40 for the week. The 2013 average diesel price was $3.85, according to AAA’s Daily Fuel Gauge Report. The state with the lowest price for gas is Missouri. The average price for gasoline is $2.24. The state with the highest national average is Hawaii with $3.70 per gallon.