We compare three forms of communication and punishment as incentives to increase contributions to public goods in laboratory experiments. We find, as in earlier experiments, that face-to-face communication has very strong effects, but surprisingly that verbal communication through a chat room preserving anonymity and excluding facial expression, etc. was almost as efficient. Numerical communication, via computer terminals, had no net effect on contributions or efficiency. Punishment, as in earlier experiments, increased contributions but because of its cost had little net effect on efficiency.

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Agents with single-peaked preferences share a resource coming from different suppliers; each agent is connected to only a subset of suppliers. Examples include workload balancing, sharing earmarked funds, and rationing utilities after a storm.Unlike in the one supplier model, in a Pareto optimal allocation agents who get more than their peak from underdemanded suppliers, coexist with agents who get less from overdemanded suppliers.Our Egalitarian solution is the Lorenz dominant Pareto optimal allocation. It treats agents with equal demands as equally as the connectivity constraints allow. Together, Strategyproofness, Pareto Optimality, and Equal Treatment of Equals, characterize our solution. © 2013 Elsevier Inc

In a moneyless market, a non storable, non transferable homogeneous commodity is reallocated between agents with single-peaked preferences. Agents are either suppliers or demanders. Transfers between a supplier and a demander are feasible only if they are linked, and the links form an arbitrary bipartite graph. Typically, supply is short in one segment of the market, while demand is short in another.Information about individual preferences is private, and so is information about feasible links: an agent may unilaterally close one of her links if it is in her interest to do so.Our egalitarian transfer solution rations only the long side in each market segment, equalizing the net transfers of rationed agents as much as permitted by the bilateral constraints. It elicits a truthful report of both preferences and links: removing a feasible link is never pro table to either one of its two agents. Together with e ciency, and a version of equal treatment of equals, these properties are characteristic.