Arrow's original proof of his impossibility theorem proceeded in two steps: showing the existence of a decisive voter, and then showing that a decisive voter is a dictator. Barbera replaced the decisive voter with the weaker notion of a pivotal voter, thereby shortening the first step, but...

This introduces the symposium on judgment aggregation. The theory of judgment ag­gregation asks how several individuals' judgments on some logically connected propo­sitions can be aggregated into consistent collective judgments. The aim of this intro­duction is to show how ideas from the...

A decision maker has to choose one of several random variables, with uncertainty known distributions. As a Bayesian she behaves as if she knew the distributions. In his paper we suggest an axiomatic derivation of these (subjective) distributions, which is much more economical than the...

A decision maker faces a decision problem, or a game against nature. For each probability distribution over the state of the world (nature's strategies), she has a weak order over her acts (pure strategies). We formulate conditions on these weak orders guaranteeing that they can be jointly...

The discounted-utilitarian social welfare function (DU) is used by the great majority of researchers studying intergenerational resource allocation in the presence of climate change (e.g., W. Nordhaus, M. Weitzman, N. Stern, and P. Dasgupta). I present three justifications for using DU: (1) the...

Attainment of rational expectations equilibria in asset markets calls for the price system to disseminate traders’ private information to others. It is known that markets populated by asymmetrically-informed profit-motivated human traders can converge to rational expectations equilibria. This...

Attainment of rational expectations equilibria in asset markets calls for the price system to disseminate agents’ private information to others. Markets populated by human agents are known to be capable of converging to rational expectations equilibria. This paper reports comparable market...

A two-house legislature can often be modelled as a proper simple game whose outcome depends on whether a coalition wins, blocks or loses in two smaller proper simple games. It is shown that there are exactly five ways to combine the smaller games into a larger one. This paper focuses on one of...

The goal of this paper is to introduce communication in a collective choice environment with information acquisition. We concentrate on decision panels that are comprised of agents sharing a common goal and having a joint task. Members of the panel decide whether to acquire costly information or...

We use a simple graphical approach to represent Social Welfare Functions that satisfy Independence of Irrelevant Alternatives and Anonymity. This approach allows us to provide simple and illustrative proofs of May's Theorem, of variants of classic impossibility results, and of a recent result on...