Ex-post ambiguity occurs when the posterior beliefs of an agent are perceived as nonunique by another agent, even if both prior beliefs are unique. We show that, in the presence of symmetrical ex-post ambiguity, agents may agree to disagree but not completely. We extend the Geanakoplos and Polemarchakis [1982]’s result about communication between agents to this situation of ex-post ambiguity, and suggest accordingly a generalized version of Geanakoplos and Sebenius [1983]’s no-trade result. Finally, we prove, most importantly, the existence of a maybe-trade in case of symmetrical full ambiguity, that is simultaneous ex-post and ex-ante ambiguity, and maxmax expected utility behavior.

We consider collective decisions under uncertainty, when agents have "generalized Hurwicz" preferences, a broad class allowing many different ambiguity attitudes, including subjective expected utility preferences. We consider sequences of acts that are “almost-objectively uncertain” in the sense that asymptotically, all agents almost-agree about the probabilities of the underlying events. We introduce a Pareto axiom which applies only to asymptotic preferences along such almost-objective sequences. This axiom implies that the social welfare function is utilitarian, but it does not impose any constraint on collective beliefs. On the other hand, a Pareto axiom for “dichotomous” acts implies that collective beliefs are contained in the closed convex hull of individual beliefs, but imposes no constraints on the social welfare function. Neither axiom entails any link between individual and collective ambiguity attitudes.

Welfare theory faces an old dilemma. On one hand, it often needs to quantify individual welfare on an interpersonally meaningful scale, notably to compare welfare across people, measure inequality, assess social welfare, and ultimately recommend social decisions. On the other hand, only purely ordinal and intrapersonal information might be available about individual welfare, be it through observed choices, self-reported welfare comparisons, or third-party assessments. We introduce and axiomatise a measure of individual welfare that is non-ordinal and inter-personally comparable while resting on purely ordinal and intra-personal information. This is achieved through five working hypotheses. We discuss arguments for and against these hypotheses. The measure helps operationalising interpersonal comparisons and (utilitarian or non-utilitarian) social evaluations. It contrasts with the standard approach of measuring welfare by Von-Neumann-Morgenstern utility.

This paper explores the possibility to replace the GDP-shareholder-value nexus, which has been under severe criticism for decades, with a combination of social-welfare compatible objectives at the macroeconomic level and at the firm level. Can GDP be replaced by social welfare and shareholder value be replaced with stakeholder value, in an integrated and consistent fashion? It is shown that money-metric utilities and their aggregation can indeed provide interesting tools to conceive of this integration of micro with macro objectives. But while consistent measures of the contribution of each firm to social welfare can be derived from this analysis, there is little hope to build new national welfare accounts in which micro-level contributions to social level could be simply added up to form social welfare at the macro level.