Efficiency and converse reduction-consistency in collective choice

We consider the problem of selecting a subset of a feasible set over which each agent has a strict preference. We propose an invariance property, converse reduction-consistency, which is the converse of reduction-consistency introduced by Yeh (2006), and study its implications. Our results are two characterizations of the Pareto rule: (1) it is the only rule satisfying efficiency and converse reduction-consistency and (2) it is the only rule satisfying one-agent efficiency, converse reduction-consistency, and reduction-consistency.consistency converse consistency efficiency Pareto rule social choice correspondences.

The effect of food intake on longevity

We investigate the startling but real possibility that a reduction in calories can lead to a increase in longevity. In perhaps the simplest model, it may be evolutionarily optimal for a permanent reduction in the food supply to cause such an increase in longevity. However, it is impossible to account for all the data if fertility is a function of the food input alone. We propose, therefore, a more flexible model, incorporating both metabolic by-products and infectious disease. Where there is little infectious disease, the only effect of decreased food is to decrease the production of metabolic by-products, so individuals have increased life expectancy. On the other hand, where infectious disease is prevalent, decreased food intake increases mortality because the resulting reduction in immune function increases the impact of the disease. These predictions are consistent with an empirical model based on income per capita and calorie intake per capita across modern nations.

Reinterpreting Mixed Strategy Equilibria: A Unification of the Classical and Bayesian Views

We provide a new interpretation of mixed strategy equilibria that incorporates both von Neumann and Morgenstern's classical concealment role of mixing as well as the more recent Bayesian view originating with Harsanyi. For any two-person game, G, we consider an incomplete information game, IG, in which each player's type is the probability he assigns to the event that his mixed strategy in G is 'found out' by his opponent. We show that, generically, any regular equilibrium of G can be approximated by an equilibrium of IG in which almost every type of each player is strictly optimizing. This leads us to interpret i's equilibrium mixed strategy in G as a combination of deliberate randomization by i together with uncertainty on j's part about which randomization i will employ. We also show that such randomization is not unusual: For example, i's randomization is nondegenerate whenever the support of an equilibrium contains cyclic best replies.

The Evolution of Decision and Experienced Utilities

Psychologists report that people make choices on the basis of "decision utilities" that routinely overestimate the "experienced utility" consequences of these choices. This paper argues that this dichotomy between decision and experienced utilities may be the solution to an evolutionary design problem. We examine a setting in which evolution designs agents with utility functions that must mediate intertemporal choices, and in which there is an incentive to condition current utilities on the agent's previous experience. Anticipating future utility adjustments can distort intertemporal incentives, a conflict that is attenuated by separating decision and experienced utilities.Discounting, Evolution, Present bias, Time preference

The evolution of decision and experienced utility

Psychologists report that people make choices on the basis of "decision utilities'' that routinely overestimate the "experienced utility'' consequences of these choices. This paper argues that this dichotomy between decision and experienced utilities may be the solution to an evolutionary design problem. We examine a setting in which evolution designs agents with utility functions that must mediate intertemporal choices, and in which there is an incentive to condition current utilities on the agent's previous experience. Anticipating future utility adjustments can distort intertemporal incentives, a conflict that is attenuated by separating decision and experienced utilities.Evolution, decision utility, experienced utility, focusing illusion

Existence of subgame perfect equilibrium with public randomization: A short proof

Consider a multi-stage game where each player has a compact choice set and payoffs are continuous in all such choices. Harris, Reny and Robson (1995) prove existence of a subgame perfect equilibrium as long as a public correlation device is added to each stage. They achieve this by showing that the subgame perfect equilibium path correspondence is upper hemicontinuous. The present paper gives a short proof of existence that focuses on equilibrium payoffs rather than paths.Existence