[영문]This paper examines the optimal allocation of risk in an overlapping-generations economy. It compares the allocation of risk the economy reaches naturally to the allocation that would be reached if generations behind a Rawlsian “veil of ignorance” could share risk with one another through complete Arrow-Debreu contingent-claims markets. The paper then examines how the government might implement optimal intergenerational risk sharing with a social security system. One conclusion is that the system must either hold equity claims to capital or negatively index benefits to equity returns.