That's what I was just going to throw in as my cautionary note. Those studies do not distinguish between marriages that were celebrated in Canada and marriages that were celebrated outside of Canada. Certainly it would appear that a large number of them were celebrated outside of Canada, so yes, that's a concern.
The other concern, of course, is that probably a number of telephone and proxy marriages were involved as well, where one of the parties would have stayed in Canada and the other would have been in another country.