To your question on the tax gap, there is no Canadian data on the tax gap. A number of jurisdictions around the world analyze what the tax gap is. The tax gap is the difference between what the government expects to collect and what they actually collect. Canada doesn't publish those figures. I assume it would be fairly similar from a Canadian perspective, but I don't know. We just don't have the data.
From my experience in a bunch of other jurisdictions, I know that the primary driver of the tax gap is the underground economy. It's those citizens who have decided that they are outside the tax system and aren't going to report income. That is by far the largest bit of the tax gap.