This paper proposes a method for the welfare analysis of pay-as-you-go social security systems. We derive a formula for the welfare consequences of a permanent marginal change in the payroll tax rate that is valid under weak assumptions about the deep structure of the economy. Our approach...

When markets are incomplete, social security can partially insure against idiosyncratic and aggregate risks. We incorporate both risks into an analytically tractable model with two overlapping generations and demonstrate that they interact over the life-cycle. The interactions appear even though...