RIVERSIDE, Calif. -

The average price of a gallon of self-serve regular gasoline in the Inland Empire dropped today for the 21st consecutive day, decreasing 1 cent to $3.978, its lowest amount since March 13.

   The average price in Riverside and San Bernardino counties has decreased  17.1 cents over the past 21 days, including seven-tenths of a cent on Monday, according to figures from the AAA and Oil Price Information Service.

   The average price is 5.8 cents less than one week ago, 15.4 cents lower than one month ago and 5.3 cents cents below what it was one year ago.

   The 21-day streak of decreases is the longest since a 24-day streak from May 2-25. The current streak was immediately preceded by 11 increases in 14 days which pushed the average price to its highest amount since May 19.

   The dropping prices are the result of increased supply stemming from refineries running at a higher capacity, according to Jeffrey Spring of the Automobile Club of Southern California.