This paper shows that improved intergenerational risk sharing in social security may imply very large welfare gains, amounting to up to 15 percent of the per-period consumption relative to the current U.S. consumption. Improved risk sharing raises welfare through a direct effect, i.e., by correcting an initially inefficient allocation of risk, and through a general equilibrium (GE) effect. The GE effect is due to the fact that the allocation of risk in the pay-as-you-go system influences the demand for capital. As a result, with an efficient risk sharing arrangement, the crowding out effect associated with an unfunded system can actually be completely eliminated. Efficient risk sharing in social security implies highly volatile and pro-cyclical benefits, i.e., that retirees’ exposure to productivity risk is increased. Consequently, a policy involving completely safe benefits will unambiguously be welfare reducing