Boy, that's a tricky question. I think one thing that's helped in recent decades is the GST. One of the reasons a lot of tax scholars support VATs and GST and international consumption taxes is that they encourage compliance, because to get your rebate, you have to file your return with the government. So there is some empirical evidence that those have helped to reduce the amount of the underground economy. It's just very tough.
My understanding is that Canada's underground economy probably compares favourably with those elsewhere, certainly with those of countries outside of the OECD, for instance. We don't have a corrupt government here. Surveys indicate that we have high taxpayer morale, in part because most taxpayers trust the system. Most of us pay. Most of us trust. This is in part why this hearing is so important, because you're encouraging a greater trust within the system, and we don't want people to bail into the underground economy.