Alternative Risk-Sharing Mechanisms of Social Security

Adopting a portfolio choice approach to pension design, we derive illuminating closed form solutions for optimal pay-as-you-go social security programs. We demonstrate that the nature of the implied risk-sharing effects and their magnitudes are sensitive to the stochastic specification of aggregate wage income growth (i.e. the implicit return on the pay-as-you-go program). Considering individuals in any generation from a "Rawlsian", prebirth perspective, fairly large pay-as-you-go programs in terms of the magnitude of the optimal contribution rate can be rationalized if wage shocks are not permanent.