Managing a pay-as-you-go pension system requires that managers choose and adjust the levers at their disposal in order to achieve the objectives they are assigned while dealing with the economic and/or demographic hazards they confront. In this framework, managers can make a commitment to precise rules, which then constrain how they manage. Three categories can be distinguished: “defined benefit” systems, where the commitment is to the amount of the pension and the adjustment is made through contributions; “defined contribution” systems, where the commitment is to the rate of the contribution and the adjustments are made to the age of liquidation or the amount of the pension; and “defined return” systems, where the commitment is to the return on the contributions so as to ensure that each generation receives the actuarial equivalent of its contributions.