Abstract
In this paper, I bring together the problems of justice between age groups and intergenerational cooperation in light of real-life demographic trends. I begin by presenting a simple model of intergenerational cooperation based on indirect reciprocity and show how cooperation can break down due to exogenous factors, including demographic change. I use the model to make the argument that principles for justice between age groups must be sensitive to the stability of intergenerational cooperation. I illustrate my thesis by considering the debate between distributive and relational egalitarians on justice between age groups.