It certainly is a cost issue. I think there are lots of disincentives for either Canada or the United States to think, in defending our shared continent, that we want to do things independently of each other. We have a long history, certainly most clearly demonstrated through NORAD, of working together. We realize we achieve a lot of equities and can also make investments in strategic redundancies together that we can't do if we're just doing things on our own. Let's face it, the cost of doing things on our own is probably going to be insurmountable or, at least, unrealistic in the short term, never mind gaining access to the technologies.
Again, I see a Canadian shield as something that has not been elaborated upon. It's been dropped as a teaser by some senior officials. I'd love for them to flesh that out more, but I see that Canadian shield, really, as being the bedrock of our contribution to this overall integrated continental effort.