We present simple and direct arguments to characterize strongly group strategy-proof social choice functions whose range is of cardinality two. The underlying society is of arbitrary cardinality, and agents can be indifferent among alternatives.

Purpose - In 1951, Kenneth Arrow proved that it is not possible to have a group decision-making procedure that satisfies reasonable requirements like fairness. From the theoretical viewpoint, this is a great result - welldeserving the Nobel Prize that was awarded to Professor Arrow. However,...

Politicians, CEOs and various other types of dictators make social choices that influence both their own and others' welfare. When a dictator's preferred alternative differs from recipients', it is unclear which preferences they aggregate and how they determine this set of admissible...

We derive a very general ("Janus") money demand function, which reflects backward and forward-looking habit formation. This generality offers an explanation for the breakdown of money-demand functions and policy relevance of monetary aggregates. Integrating our Janus money demand into a...

Consider a setting in which individual strict preferences need to be aggregated into a social strict preference relation. For two alternatives and an odd number of agents, it follows from May’s Theorem that the majority aggregation rule is the only one satisfying anonymity, neutrality, and...

Can the exchange rate be stationary in levels? We answer this question in the negative by proving an impossibility theorem, built upon the absence of arbitrage in international economies. We establish the sufficient conditions for the exchange rate to not be a stationary process in levels, and...

Some economists in the Austrian tradition interpret the Arrow Impossibility Theorem (AIT) as support for their laissez-faire standpoint. They presume that the AIT cannot be applied in market settings, but in the context of voting, it adds weight to their arguments against the possibility of...

The economist Kenneth J. Arrow, in Social Choice and Individual Values (1951), famously proved that a society of diverse preferences can only be ordered by dictatorship. As individual preferences are distinct, then given certain reasonable conditions, no ordering of them is feasible through...

Arrow's theorem proves that no voting procedure can meet certain conditions of both fairness and logic. In this note, Grant Hayden explores the ramifications of the theorem for qualitative vote dilution. After describing Arrow's argument, Mr. Hayden considers four democratic voting procedures...

We know that a strategyproof mechanism does not exist that is ordinally efficient and fair in the sense of equal division lower bound. We show that this impossibility for random assignments prevails even if agents have uniform preferences where a weakly decreasing utility function determines...

We model a situation where a set of agents must rank themselves based on their opinions. Each agent submits a message and a function determines the social ranking. We are interested in impartial social ranking functions, that is, those where the message of an agent can not change any social...

We model a situation where a set of agents must rank themselves based on their opinions. Each agent submits a message and a function determines the social ranking. We are interested in impartial social ranking functions, that is, those where the message of an agent can not change any social...

Environments with semi-ordered preferences, which may exhibit indifference intransitivity, are known to allow just-noticeable differences in preference intensity to serve as interpersonally comparable units of utility. I prove two impossibility theorems for social choice in such environments....

We know that ex-post Pareto efficiency is possible with strategy-proofness and weak envy-freeness while ordinally efficiency is incompatible with them. We strengthen this impossibility for random assignments and show that it prevails if ordinal efficiency is weakened to robust ex-post Pareto...

The problem of social choice is studied on a domain with countably many individuals. In contrast to most of the existing literature which establish either non-constructive possibilities or approximate (i.e. invisible) dictators, we show that if one adds a continuity property to the usual set of...

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...

Abstract: Since the 18th century, doubt has been raised concerning “rational” majoritarian public choice: the “voting paradox” holds, in a simple calculation made famous by the Marquis de Condorcet, that rational resolution of divergent preferences by voting is impossible. The economist...

Judgments are the basis for almost all decisions. They often come from different models and multiple experts. This information is typically aggregated using simple averages, which leads to the well-known shared information problem. A weighted average of the individual judgments based on...