Thanks for the clarification on the US version of RRSPs....I haven't lived in the US since I was 11 years of age, and my paper route didn't have any retirement savings investment options.

As for RRSPs here in Canada....whether its a group plan or self directed, there is an annual limit that's based on income.  Its 18% of your income to a max of $26,300 (I just checked).  Those who contribute to a pension and/or a group RSP plan, the individual contribution limit is adjusted down.  Someone with 26K in annual contribution room....if they're in a work plan in which they put in funds that are matched....then those contributions are deducted, same thing with a pension. 

Unused contribution room from previous years does accumulate...when a Canadian files taxes, after filing they receive a statement from CRA, a notice of assesement.  That notice tells you what your contribution limit is for the coming year.  When I file my 2018 taxes in a few week....some weeks later I'll get my notice and it will tell me the maximum allowable contribution room I'll have for the year 2019.

Gonna check the short interest.