In fact, the Copyright Act makes it possible to establish a percentage, by regulation, if I'm not mistaken. I had the opportunity to testify on this subject when I appeared before the committee as president of the Canadian Private Copying Collective. It is possible to limit the amount, to set a ceiling. I believe it would be possible to establish a percentage, if that was what the government wanted.
On March 10th, 2011. See this statement in context.