I'll just add quickly to give an example of what this looks like.
A Ph.D. student in the United States right now with an NSF grant will make $65,000. The awards in Canada are $21,000. That alone is going to drive people away.
The National Institutes of Health gives a $52,000 salary for a Ph.D. student and a $70,000 to $85,000 salary for a post-doc. This is uncomparable to Canada. This is nearly double the salary, so it makes sense that they're not staying in Canada.