68% of Canadians use cannabis?
It is probable that 68% of Canadians smoke or use cannabis in some form. It doesn't come across in polling data where people must self-report criminal behaviour, especially if it may be possible to identiy them in some way (like phone surveys), but it's out there.
The assumption/thesis is some people will never self-report criminal behaviour and will lie on any survey, report, unless caught red-handed somehow, so it includes all closet consumers, liars and other unreported.
There is no way to really prove which is more truthful - my hunch or science, so anecdotal experience is likely your best guide.
Notice the numbers when those surveyed are not implicating themselves, but somone else.
In Fig. A the poll gathers what users feel is fairly anonymous data that mirrors the data above, but as is often the case, the word gets out in various circles, then the random data becomes skewed. Fig. B
Polls used to always be skewed in favour of reform as most of the websites were also in favour of reform. By mid-decade, the status quo knew they must step up their efforts and presence on the internet, so today you can see polls skewed either way - depending on which side of an issue gets the word out. Whether it is 68% or 50%, it is a sizeable amount of the population not reflected in less anonymous surveys, but reflected in real lives.
The world drug-use study by the UN Office on Drugs and Crime said that 16.8% of Canadians aged 15 to 64 smoked marijuana or used other cannabis products in 2004, the most recent year for which statistics were cited. 2004: [Source]
According to research commissioned by Health Canada, a survey of 12-to 19-year-olds conducted this fall found that 34% said they had tried marijuana on more than one occasion. 2003: [Source]
A study done last year by the Canadian Medical Association showed only 6.8% of people surveyed in Ontario had used the drug (cannabis) in the preceding year for recreation - only 1.9% had used it for a medical condition. 2001: [Source]