We haven't provided evidence on that because most of the data comes from Statistics Canada. There's no point in duplicating efforts.
I do, however, want to caution people on interpretation of the data. In science, there's always been mobility among countries, and certainly between the U.S. and Canada. People go from Canada to the U.S. to do post-doctoral training, for example. Sometimes they don't come back, but sometimes they come back. U.S. and other citizens come to work here.
We have to be very careful when we analyze brain-drain and brain-gain data. I just wanted to mention that.