Nearly all modern public pension programs involve a substantial transfer of wealth from workers to retirees. If parents love their children, why are these intergenerational transfers politically sustainable? This paper develops a cross-national overlapping generations model to explore the impact of income mobility on the way workers and retirees calculate the long-term value of these programs to their children. Mobility affects their evaluations because these programs also redistribute intragenerationally. The analysis shows why a majority of rational voters who care about their descendants can insist on the preservation of current public pension benefits for themselves but accept a future reduction. Implications of this explanation are tested using comparative intergenerational mobility data and a 2001 Eurobarometer survey on pensions.