It's time of day and time of year and the fact that in B.C. you have good hydro storage. But, in general, the trade of electricity is very dynamic and there's not one U.S. market; there are several. So B.C. interconnects with the western market; Ontario is into the midwest ISO and New York; and Quebec is into either New England or New York. In that case, they all interact, and it's traded depending on the market prices by hour. It's actually traded by hour.
B.C. had a net surplus of just under three terawatt hours last year, and I think the year before it was actually a net importer. It had a really high water year, so it had an opportunity. In B.C. there's an interplay with Alberta next door to it, a 300-megawatt tie, as well as into Washington State and all the way down to California.
That just reflects various times of the year, times of day, how much water is available, how much can be stored, and what electricity prices are. For B.C. Hydro, through Powerex, if they see market prices are really low in the U.S., they'll actually buy it, store it, and then sell it when prices are high.