The state’s latest gas price survey finds pump prices jumped 23 cents in the past month. David Downing of the Iowa Department of Natural Resources says the average price is a dollar-63 per gallon for self-serve unleaded.Surveyors found a low of a buck-55 — and a high of a dollar-80. Downing says there’s not normally such a difference in Iowa gasoline prices. He says the market is more volatile now than what it has been as the prices switch. There are three thousand gasoline retailers in Iowa.