When people put money into an RRSP, the government loses tax revenue in that year, but there's no way to get the money out. The money will come out some day, maybe 20 years from now, but when the money comes out it's going to be taxed at a good, healthy rate.
Quand les gens mettent de l'argent dans un REER, le gouvernement perd des recettes fiscales cette année-là mais il les récupère plus tard, à un taux d'imposition fort satisfaisant, dans 10, 15 ou 20 ans, lorsque l'argent sort du REER.