  This paper examines the representation and explicit description of social
welfare orders on infinite utility streams. It is assumed that the social
welfare orders under investigation satisfy upper asymptotic Pareto and
anonymity axioms. We prove that there exists no real-valued representation of
such social welfare orders. In addition, we establish that the existence of a
social welfare order satisfying the anonymity and upper asymptotic Pareto
axioms implies the existence of a non-Ramsey set, which is a non-constructive
object. Thus, we conclude that the social welfare orders under study do not
admit explicit description.
