The fact that those taxes are currently collected by the stock exchange does not mean that they are not collected. It only means that the administrative overhead is greater, and introduces a couple of extra middlemen who have to get a cut.
- Jake If you only spend 20 minutes of the rest of your life on economics, go spend them here.
But I have to finance the pensions with my taxes anyway.
No you don't, and with a system where everyone (forcibly) saves money for her own account, you do not have to deal with the intergenerational problems and imbalances arising from a change in the age structure.
No pension fund stockpiles wheat in big silos in the harbour for distribution to retirees. What they stockpile is claims over value. The goods still have to be produced when those claims over value are to be redeemed. Whether those goods are claimed as profits for a pension fund portfolio or as taxes for the government makes little difference to the person who produces them, except inasmuch as government pensions have considerably lower overhead costs.