Non-bossy Social Classification

We consider the problem of how societies should be partitioned into classes if individuals express their views about who should be put with whom in the same class. A non-bossiness condition makes the social aggregator dependent only on those cells of the individual partitions the society members classify themselves in. This information is used to construct for each profile of views an opinion graph. By means of natural sovereignty and liberalism requirements, we characterize the non-bossy aggregators generating partitions in which the social classes are refinements of the connected components in the opinion graph.Social Aggregation, Group Identity, Liberalism, Non-bossiness

Non-bossy social classification

We consider the problem of how societies should be partitioned into classes if individuals express their views about who should be put with whom in the same class. A non-bossy social aggregator depends only on those cells of the individual partitions the society members classify themselves in. This fact allows us to concentrate on a corresponding 'opinion graph' for each profile of views. By means of natural sovereignty, liberalism, and equal treatment requirements, we characterize the non-bossy aggregators generating partitions in which the social classes are refinements of the weakly connected components of the opinion graph. --social aggregation,group identity,liberalism, non-bossiness

STRATEGY-PROOF MECHANISMS WITH PRIVATE AND PUBLIC GOODS

In this paper we develop a differentiable approach to deal with incentives in a, possibly small, subset of a general domain of preferences in economies with one public and one private good. We show that, for two agents, there is no social rule which is efficient, nondictatorial and strategy-proof. For the case of more agents the same result occurs when nondictatorship is replaced by Individual Rationality or by Envy-Freeness. Journal of Economic LiteratureStrategy-proofness, public goods economies, differentiable mechanisms

Allocation by coercion

The problem of allocating indivisible goods is considered when groups of individuals can make use of their power to plunder other groups. A monarch in a group of individuals is an individual who always obtains one of his most preferred goods. A Paretian condition together with a requirement of robust stability lead to the existence of monarchs in all subsets of individuals, except possibly one.Allocation rule; dictator; indivisible good; power; coalition formation.

Secure implementation

Strategy-proofness, requiring that truth-telling be a dominant strategy, is a standard concept in social choice theory. However, this concept has serious drawbacks. In particular, many strategy-proof mechanisms have multiple Nash equilibria, some of which produce the wrong outcome. A possible solution to this problem is to require double implementation in Nash equilibrium and in dominant strategies, i.e., secure implementation. We characterize securely implementable social choice functions and investigate the connections with dominant strategy implementation and robust implementation. We show that in standard quasi-linear environments with divisible private or public goods, there exist surplus-maximizing (non-dictatorial) social choice functions that can be securely implemented.Nash implementation, robust implementation, secure implementation, strategy-proofness

Fairness and group-strategyproofness clash in assignment problems

No group-strategyproof and ex-post Pareto optimal random matching mechanism treats equals equally. Every mechanism that arises out of the randomization over a set of non-bossy and strategyproof mechanisms is non-bossy. Random serial dictatorship, which arises out of a randomization over all deterministic serial dictatorships is non-bossy but not group-strategyproof

Secure Implementation

Strategy-proofness, requiring that truth-telling is a dominant strategy, is a standard concept in social choice theory. However, this concept has serious drawbacks. In particular, many strategy-proof mechanisms have multiple Nash equilibria, some of which produce the wrong outcome. A possible solution to this problem is to require double implementation in Nash equilibrium and in dominant strategies, i.e., secure implementation. We characterize securely implementable social choice functions, and compare our results with dominant strategy implementation. In standard quasi-linear environments with divisible private or public goods, there exist Pareto efficient (non-dictatorial) social choice functions that can be securely implemented. But in the absence of side-payments, secure implementation is incompatible with Pareto efficiency.