Okay, I understand how it works. And I understand that higher prices mean more profit. What I don't understand is the behavior that they are trying to drive. Is it just that they want people to book early? I keep looking at the prices for next summer for our trip. And they are very interesting to watch how they change (go up and go down as people must cancel or change their dates). If you have flexible travel dates, most people would pick the cheapest one, I'd expect. So aren't they driving people signing up for a lot of different trips (spreading the guests around and making it more likely that trips will be cancelled), instead of working to fill some of them and then adding more. Or are they just genius - because they sell out all of the time?