I want to jump in. Earlier you asked a question about what would happen if there were a voluntary CPP supplement, which would be on a defined contribution basis. It's going to suck money out from the RRSP contributions people would have otherwise made.
There's a very important point here. One of the biggest drops in people's retirement incomes is the expense ratio charged for the ability to get any investment income. Many people don't understand how to invest their RRSPs, so they tend towards fairly high-cost vehicles. If you have a voluntary supplement to the Canada Pension Plan, it could be run, theoretically, at a much lower expense ratio. The impact would be huge.