The U.S. national average price for a gallon of regular unleaded gasoline could fall another 16 cents to $2.50 by Christmas, motor club AAA said. AAA reports a national average price for Tuesday at $2.66, down 10 cents from one week ago and off more than 60 cents from this date in 2013. The motor club said that, for the year, prices are off more than $1 per gallon from their April peak of $3.70 "Plentiful global crude oil supplies continue to be a primary contributing factor to falling averages nationwide," AAA said in a Monday market brief. High supplies and low demand in a weak global economy translates to lower crude oil prices, which account for about 60 percent of the price consumers see at retail filling stations. AAA said the national average price could drop further to hit the $2.50 per gallon mark by Christmas. Already, gasoline prices are declining to the point they may be at their lowest since 2009 "in a matter of days." But the motor club cautioned there is a floor for the national average price per gallon. Oil prices would need to shed at least $25 more per barrel for the national average to reach $2 per gallon. Last year's annual average price was $3.51 per gallon. The U.S. Energy Information Administration EIA said it expects an average $3.39 per gallon for 2014. For full-year 2015, the average price for a gallon of regular unleaded should be $2.94 per gallon.