Sidartha Gordon

Public decisions: Solidarity and the status quo

A public decision model specifies a fixed set of alternatives A, a variable population, and a fixed set of admissible preferences over A, common to all agents. We study the implications, for any social choice function, of the principle of solidarity, in the class of all such models. The principle says that when the environment changes, all agents not responsible for the change should all be affected in the same direction: either all weakly win, or all weakly lose. We consider two formulations of this principle: population-monotonicity (Thomson, 1983); and replacement-domination (Moulin, 1987). Under weak additional requirements, but regardless of the domain of preferences considered, each of the two conditions implies (i) coalition-strategy-proofness; (ii) that the choice only depends on the set of preferences that are present in the society and not on the labels of agents, nor on the number of agents having a particular preference; (iii) that there exists a status quo point, i.e. an alternative always weakly Pareto-dominated by the alternative selected by the rule. We also prove that replacement-domination is generally at least as strong as population-monotonicity.

Solidarity in Choosing a Location on a Cycle

We study the implications of two solidarity conditions on the efficient location of a public good on a cycle, when agents have single-peaked, symmetric preferences. Both conditions require that when circumstances change, the agents not responsible for the change should all be affected in the same direction: either they all gain or they all loose. The first condition, population-monotonicity, applies to arrival or departure of one agent. The second, replacement-domination, applies to changes in the preferences of one agent. Unfortunately, no Pareto-efficient solution satisfies any of these properties. However, if agents’ preferred points are restricted to the vertices of a small regular polygon inscribed in the circle, solutions exist. We characterize them as a class of efficient priority rules.

Unanimity in attribute-based preference domains

We provide several characterizations of unanimity decision rules, in a public choice model where preferences are constrained by attributes possessed by the alternatives (Nehring and Puppe, Games Econ Behavior 59:132–153, 2007a; Nehring and Puppe, J Econ Theory 135:269–305, 2007b). Solidarity conditions require that when some parameters of the economy change, the agents whose parameters are kept fixed either all weakly lose or they all weakly win. Population-monotonicity (Thomson, Math Oper Res 8:319–326, 1983a; Thomson, J Econ Theory 31:211–226, 1983b) applies to the arrival and departure of agents, while replacement-domination (Moulin, Q J Econ 102:769–783, 1987) applies to changes in preferences. We show that either solidarity property is compatible with voter-sovereignty and strategy-proofness if and only if the attribute space is quasi-median (Nehring, Social aggregation without veto, Mimeo, 2004), and with Pareto-efficiency if and only if the attribute space is a tree. Each of these combinations characterizes unanimity.

Project Selection: Commitment and Competition

We examine project selection decisions of firms constrained in the number of projects they can handle at once. A new project opportunity arises every period. Taking on a project requires a commitment of uncertain duration, preventing the firm from selecting another project in subsequent periods until the commitment ends. In our dynamic game, when two firms are free of commitment, they move sequentially in random order. Symmetric pure strategy Markov perfect equilibria always exist. In equilibrium, the first mover strategically rejects some projects that are then selected by the second mover, even when the value of the project is the same for both firms. A monopolist rejects more projects, and adopts ones of higher average quality compared to the duopolist. Duopolists select too few projects compared to their jointly optimal behavior. We extend the model to allow for externalities, asymmetry, and n>2 firms.

Doubts and Dogmatism in Conflict Behavior

This paper studies a game of conflict where two individuals fight in order to choose a policy. Intuitively, conflicts will be less violent if individuals entertain the possibility that their opponent may be right. Why is it so difficult to observe this attitude? To answer this question, this paper considers a model of indoctrination where altruistic advisors (such as, preachers or parents), after receiving signals from Nature, send messages to the participants in the conflict. In some cases, as a result of indoctrination, both individuals never doubt about the possibility of being wrong, although all available information suggests otherwise. In other cases, one of the two individuals is excessively reasonable: he believes that the opponent may be right even when all the evidence indicates beyond any doubt that the policy preferred by the opponent is suboptimal. The common feature in both cases is that information is distorted, although in different directions. The model has a rich set of predictions concerning the incidence and intensity of conflict, and the evolution of indoctrination strategies over time.

Doubts and dogmatism in conflict behaviour

We consider a conflict under incomplete information where two opponents fight to impose their preferred policy. Before the conflict, one opponent (the agent) trusts the information received by his principal. Under some conditions, the principal induces hawkish attitudes in the agent: the agent never doubts the optimality of his preferred policy, conflicts are violent, and bad decisions are sometimes made. Under other conditions, the agent believes that his opponent may be right, even when all evidence indicates that the policy preferred by the opponent is certainly suboptimal. In this case, the agent adopts dovish attitudes and conflicts are less violent.