This is a very tricky thing to analyze, because you're looking at all kinds of reasons and the data, etc. To the extent that we have been able to dig down into these issues, there does not seem to be a wage issue. The wage advertised is supposed to be the median wage for Canadians, so the same wage is being paid. What's being offered to the temporary foreign worker is the same as what's being offered to Canadians.
On October 31st, 2017. See this statement in context.