Sure. Generally, at most earnings levels, there is unused RRSP room, meaning that people are not constrained by the limit. At the middle and lower earnings levels, it's even over 90% of people who have unused RRSP room. So not very many, less than 10%, are constrained by the 18% limit. That goes down a bit at the higher earnings levels but still, there are quite a few earners with unused RRSP room. If you're looking at over $125,000, about 70% of those people have unused RRSP room, so again it's a minority who are constrained by the maximum limits.
On November 3rd, 2009. See this statement in context.