Limit representations of intergenerational equity

Equal treatment of all generations is a fundamental ethical principle in intertemporal welfare economics. This principle is expressed in anonymity axioms of orderings on the set of infinite utility streams. We first show that an ordering satisfies finite anonymity, uniform Pareto, weak non-substitution, and sup continuity if and only if it is represented by an increasing, continuous function that is a natural extension of the limit function. We then show that whenever such an ordering is infinitely anonymous, it depends only on the liminf and limsup of any utility stream. Our results imply that in ethically ranking utility streams, reflecting only infinitely long-run movements is possible, with liminf and limsup particularly essential, but it is impossible to respect finite generations.