Time-inconsistent preferences and time-inconsistent policies

Social security is commonly viewed as a commitment device for hyperbolic consumers. We argue that such common intuition is not consistent with formal economic theory. In a model where the government can choose either time-consistent or time-inconsistent policies to govern its social security arrangement and credit markets are complete, only a time-inconsistent policy achieves true commitment by hyperbolic consumers. This rules out a traditional social security program as a commitment device.