Topological effects produce chaos in multiagent simulation and distributed computation. We explain this result by developing three themes concerning complex systems in the natural and social sciences: (i) Pragmatically, a system is complex when it is represented efficiently by different models at different scales. (ii) Nontrivial topology, identifiable as we scale towards the global, induces co...

In a seminal contribution, Hansson (1976) demonstrates that the collection of decisive coalitions associated with an Arrovian social welfare function forms an ultrafilter. He goes on to show that if transitivity is weakened to quasi-transitivity as the coherence property imposed on a social relation, the set of decisive coalitions is a filter. We examine the notion of decisiveness with acyclica...

There exists a utilitarian tradition à la Sidgwick of treating equal generations equally in the form of anonymity. Diamond showed that no social evaluation ordering over infinite utility streams satisfying the Pareto principle, Sidgwick’s equity principle, and the axiom of continuity exists. We introduce two versions of egalitarianism in the spirit of the Pigou-Dalton transfer principle and the...

I analyze the effect of a sequential election system when the first voter has private information using a simple two candidate, two voter model in which the second voter is decisive. Both voters observe the candidates’ policy positions, but only the first voter observes which candidate is competent. I show that in equilibrium the candidates pander to the policy preferences of the first voter. D...

The fact that many people take it upon themselves to impose costly punishment on free riders helps to explain why collective action sometimes succeeds despite the prediction of received theory. But while individually imposed sanctions lead to higher contributions in public goods experiments, there is usually little or no net efficiency gain from them, because punishment is costly and at times m...

A class of voting procedures based on repeated ballots and elimination of one candidate in each round is shown to always induce an outcome in the top cycle and is thus Condorcet consistent, when voters behave strategically. This is an important class as it covers multi-stage, sequential elimination extensions of all standard one-shot voting rules (with the exception of negative voting), the sam...

Lotteries vs. All-Pay Auctions in Fair and Biased Contests The form of contests for a single fixed prize can be determined by a designer who maximizes the contestants’ efforts. This paper establishes that, under common knowledge of the two asymmetric contestants’ prize valuations, a fair Tullock-type endogenously determined lottery is always superior to an all-pay-auction; it yields larger expe...

This paper deals with the problem of incentive mechanism design in non-convex production economies when production sets and preferences both are unknown to the designer. We consider Nash-implementation of loss-free, average cost, marginal cost, voluntary trading, and quantity-taking pricing equilibrium allocations in economies involving increasing returns to scale or more general types of non-c...

We develop a de nition of equilibrium for agenda formation in general voting settings. The de nition is independent of any protocol. We show that the set of equilibrium outcomes for any Pareto eÆcient voting rule is uniquely determined, and in fact coincides with that of the outcomes generated by considering all full agendas. Under voting by successive elimination (or amendment), the set of equ...

We define secure implementation with partially honest agents in a social choice model and we show that strategy-proofness is a necessary and sufficient condition for it. This result offers a behavioral foundation for rectangularity ; and it remains valid even with only one partially honest agent. We apply the concept to a single-crossing voting environment, and we prove that it characterizes th...