The average U.S. gasoline price dropped by more than 11 cents per gallon over the past three weeks as an oversupply of gasoline worked in consumers’ favor, according to a new nationwide survey.

The price of self-serve regular dipped to $2.72 per gallon in the latest edition of the Lundberg Survey, a drop of 11.26 cents per gallon from early May 21, survey publisher Trilby Lundberg told CNN Sunday.

Spurred in part by falling crude prices, gas prices fell 20.51 cents in the past five weeks.

In short, demand has been down and supply has increased, leading to drop in price, Lundberg said.

“An imbalance between supply and demand is in favor of consumers,” she said.

Persistent unemployment and underemployment has contributed to the decreased demand, while refineries have been churning out more gas because they are hungry for sales, Lundberg said.

However, in recent days, crude prices have increased. If they continue, it could stop the downward slide of prices and even increase them, she said.

The highest gas prices in this week’s survey were in San Francisco, California, at $3.10 per gallon. The lowest were in Jackson, Mississippi, at $2.43.

A sampling of average prices in other U.S. cities:

Houston, Texas: $2.52

Atlanta, Georgia: $2.58

Phoenix, Arizona: $2.63

Denver, Colorado: $2.58

Chicago, Illinois; $2.91

Boston, Massachusetts: $2.76

Seattle, Washington: $2.97

(Source: CNN)