It depends on the jurisdiction. There are cultural differences around the world in taxation and in respect of the obligation of the citizen to pay. In Japan, everybody pays their tax because it's the right thing to do. In a lot of other jurisdictions, there's a massive underground economy. Greece is one that's often cited.
I'd like to think Canadians are generally very compliant with the income tax system. My belief is that there is a much smaller problem regarding the underground economy than what we'd see in other jurisdictions around the world.