Average retail gasoline prices in Des Moines have fallen 3.1 cents per gallon in the past week, averaging $3.76 per gallon on Sunday; the national average has increased 2.8 cents per gallon in the last week to $3.83 per gallon, according to gasoline price website DesMoinesGasPrices.com. Including the change in gas prices in Des Moines during the past week, prices yesterday were $1.03 higher than on the same day one year ago and 25.6 cents per gallon higher than a month ago. The national average has increased 28.1 cents per gallon during the last month and stands 97.9 cents per gallon higher than this day one year ago.