Dr. Mike Walden, North Carolina Cooperative Extension economist in the College of Agriculture and Life Sciences at N.C. State University, responds:

"Of course, there are a lot of potential explanations floating around. Some say speculation. Some say the oil market is rigged. But as an economist, I look for economic explanations, and one of my colleagues, economist James Hamilton, has, I think, come up with a very concise view of what has happened in the oil market over the last decade. He said first of all that we had the tremendous run up in oil prices for a simple reason, we've had a big increase in demand, particularly from countries like China and India. And because oil supplies were not increasing at the same rate, you had to have an increase in price in order to get some people in the world - like you and me - to reduce our consumption. And because we aren't able to reduce our consumption very much in the short run, you had to have a big increase in price. Now, as far as the reduction in oil prices, he said again, it's a result of demand, this time a decrease in demand brought on by the worldwide recession. However, prices have not come down as far as they went up simply because now people don't need to have as big a drop in oil prices in order to expand their demand because in the long run our response to price change is greater as we have more time to adapt. So I think his point here is that it's really simple economics. You don't have to go far beyond Econ 101 to explain the big changes we've seen in oil prices."