I'm sure Dr. Turnbull also has some statistics on this, but I believe your vote is determined based on your last residency, so you have to prove to Elections Canada where you last resided.
The real question and the problem here is with Canadians who have been away from Canada for a very long time. Obviously, there are those like me who have been abroad for a short amount of time. I know exactly what my riding is and I know exactly where I'm supposed to put my address. It's really about the portion of external voters who have been abroad for 20 or so years and are no longer really connected to their riding.
Again, overall, what is the actual percentage of outside voters who fall into that category? The truth is that we don't really have data on that. We don't know how many of those voters are the voters who have been abroad for too long.
To properly answer that question, first we should have a bit more data. Certainly, I wouldn't think it applies to everyone. I think it applies to a very specific subsection of those voters.