Every agent reports his willingness to pay for one unit of a good. A mechanism allocates goods and cost shares to some agents. We characterize the group strategyproof (GSP) mechanisms under two alternative continuity conditions interpreted as tie-breaking rules. With the maximalist rule (MAX) an...

We prove a general possibility result for collective decision problems where individual allocations are one-dimensional, preferences are single-peaked (strictly convex), and feasible allocation profiles cover a closed convex set. Special cases include the celebrated median voter theorem (Black...

We develop an analysis of voting rules that is robust in the sense that we do not make any assumption regarding voters' knowledge about each other. In dominant strategy voting rules, voters' behavior can be predicted uniquely without making any such assumption. However, on full domains, the only...

We study ex post implementation in collective decision problems where monetary transfers cannot be used. We find that deterministic ex post implementation is impossible if the underlying environment is neither almost an environment with private values nor almost one with common values. Thus,...

We present the results of a new laboratory experiment designed to mimic the ways in which credit bureaus will alter microfinance markets. Where loans are taken in groups, bureaus can build reputations for borrowers at the group or the individual level, and the optimal contract is not obvious. In...

In a range of settings, private firms manage peer effects by sorting agents into different groups, be they schools, communities, or product categories. This paper considers such a firm, which controls group entry by setting a series of anonymous prices. We show that private provision...

In a range of settings, private firms manage peer effects by sorting agents into different groups, be they schools, communities, or product categories. This paper considers such a firm, which controls group entry by setting a series of anonymous prices. We show that private provision...

In a range of settings, private firms manage peer effects by sorting agents into different groups, be they schools, communities, or product categories. This paper considers such a firm, which controls group entry by setting a series of anonymous prices. We show that private provision...

The paper considers a voting model where each voter's type is her preference. The type graph for a voter is a graph whose vertices are the possible types of the voter. Two vertices are connected by an edge in the graph if the associated types are "neighbors." A social choice function is locally...

The implementation problem is the problem of designing a mechanism (game form) such that the equilibrium outcomes satisfy a criterion of social optimality embodied in a social choice rule. If a mechanism has the property that, in each possible state of the world, the set of equilibrium outcomes...