As you point out, there is a direct connection between the measurement of the overall debt-to-GDP ratio, in particular the revenues the government collects, and tax havens.
As is well established by the reports we've published in the past, as well as those of the Canada Revenue Agency and other jurisdictions, there is a sizable tax gap in most developed countries, including Canada. That results in a situation of—I believe my predecessor used the number “billions”—billions of dollars that potentially go uncollected.
I believe the Canada Revenue Agency has also published several reports on the tax gap that used the term “billions” as well.