You know what? The lack of data in this G7 country really drives me crazy, so I'm going to give you proxy answers.
In the world of the polytechnics, some 25% of our post-secondary students are reporting prior post-secondary experience. Some 15% are reporting prior university degrees, but in the trades piece, I don't have it as a whole. I can't speak for the whole country, but you'd have to figure that they've done something else before they decided to sign up and become an apprentice at the age of 26.
The bigger problem, though, is also why we are not talking about how long this will take to complete. If you start at 26 and there are four levels of apprenticeship, you're going to be 30 or 32 before you get your ticket, and some of this is pretty labour-intensive work. That's the completion issue that was raised earlier.
We really need better data. Statistics Canada gives you an annual snapshot of how many apprentices are registered. That doesn't mean anything, because you could have registered but not be pursuing your trade. It only surveys apprentices every seven or 10 years. We need better real-time data about the different pathways.
Your question is right. I wish I could answer you. We can give you some proxy answers.