The pension system in Estonia consists of a shared fund "First Pillar" and an individual specific fund "Second Pillar". Part of your salary goes into the pension system and gets split between these two funds.

So the current workforce is helping to keep up the First pillar for the current pensioners. But at the same time the current workforce is making deposits into the Second Pillar which just invests their money into the markets.

So people can liquidate their Second Pillar without messing up the First Pillar for everyone else.