Our view on that is largely that on the crude oil side we have an extraordinarily well-integrated and efficient North American market. It's not perfect, obviously, but it is unusually well integrated by global standards. Most of the time those transactions are happening in a relatively efficient manner.
Issues of distance to market and size of market drive much of that export to the United States. There's a fair amount of Canadian oil coming to central Canada. There's also a tremendous amount of Canadian oil going to the northern midwest, relatively proximate, and into the western U.S. I think it's largely driven by efficiencies related to transport costs.