Behind any measurement of intergenerational justice, there is an underlying theory. Any such theory will require two crucial decisions. One is about the meaning of generation – age groups or birth cohorts. An age group is a group of those having reached the same age. It is in this sense that young and old belong to different generations. A birth cohort is a group of those born at the same time. Millennials and Baby Boomers are different generations in this second sense. Under the first meaning, we constantly change generation throughout our lives, from youth to old age. Under the second, however, we belong all our life to a single generation.
Another important decision is what we mean by justice. Among other options, we can choose here between a more commutative conception, typically involving the idea of reciprocity, or a more distributive one. Commutative theories focus on fairness in exchange. They often say: “Because I give this, I should receive that in return”. In contrast, distributive views are concerned with fairness in the background distribution between parties. From this perspective, my entitlement to some benefit is not based on having contributed something in the first place. Instead, it is based, for example, on the fact that I am a human being who deserves to be treated fairly and that I find myself in a more disadvantaged position (in the case of egalitarianism, for instance).
It is common for measurements of intergenerational justice to focus on justice as reciprocity and on generations as age groups. In this paper, we explore possible drivers of this situation and the problems it can generate. We then show that the indicators proposed in this project can help us measure intergenerational injustice, even on an approach that is neither centered on reciprocity nor restricted to age groups.