Higher commodity prices might be the rule rather than the exception in the coming years, a Purdue University agricultural economist says.

While prices regularly rise and fall, they have trended upward in a way that suggests they've reached a plateau, said Mike Boehlje. He attributed much of the price movement to bullish export markets, weather-shortened supplies and the effect monetary policies have had on interest rates and investors.

"This higher level may be the new normal," Boehlje said.

"But volatility has increased significantly for agricultural prices, as well as for agricultural inputs. In terms of corn, for example, it's not unusual in the futures markets to see prices moving 30 cents or more on a daily basis. And although prices may be higher, so are costs to producers. So margins are not likely to stay unusually high."

Corn and wheat in recent weeks have been trading in the range of $6-$7 per bushel and soybeans above $13 a bushel, about double the prices five years ago.

The strong prices are not driven just by weather and shortage of crops. A major cause of surging prices is global demand for food.

While agricultural exports always have been a mainstay of the U.S. economy, they have taken on even greater prominence as personal incomes grow in developing nations, Boehlje said. Along with having more money to spend, people in those nations are demanding more and better food.

"There's been a very rapid growth of income in Asia and, particularly, China," Boehlje said. "They've been very aggressive in buying food and trying to improve their diets. That was a big part of why agriculture in the United States didn't have the same level of pain from the recession as most of the rest of the U.S. economy."