I would add that I think sometimes we imagine the missile defence system as infinite ammunition, and if a missile is coming in we can just keep firing and knocking those missiles down. Even in the United States the reality is we have a limited number of bullets in the gun, if you will. We have a limited number of shots. Going back to my comment earlier, citing Professor Sokolsky's view that Canada's is, at its best, an easy rider, we don't want a situation where the United States is investing to put in missile defences to protect Americans and Canadians, and they have to make a choice. If Canada doesn't participate in the system, and because Canada isn't adding bullets to the gun, the U.S. has to make a choice between protecting Los Angeles or Vancouver from a North Korean missile.
What we need is for Canada to contribute in this way, so that it's able to hold up its own. With limited defence resources, even with the U.S. defence budget, we're not investing foolishly, but getting the best defence we can by sharing the burden a little.