Now to the Department of Natural Resources officials. I'm looking at slide 10 of the slides you had there, and it seems to me that the retail margin cost stays very, very close to the line. You referred to the cyclical nature of the refining margin costs, but I'm not sure I heard a reason for why it's so cyclical. It does seem as if it goes up and down pretty substantially, but I'm not sure I understand the reasons why that happens.
