Double Implementation in a Market for Indivisible Goods with a Price Constraint

I consider the problem of assigning agents to objects where each agent must pay the price of the object he gets and prices must sum to a given number. The objective is to select an assignment-price pair that is envy-free with respect to the true preferences. I prove that the proposed mechanism will implement both in Nash and strong Nash the set of envy-free allocations. The distinguishing feature of the mechanism is that it treats the announced preferences as the true ones and selects an envy-free allocation with respect to the announced preferences.Indivisible Goods, Envy-Freeness, Implementation, Strong Nash Equilibrium

Repeated implementation with overlapping generations of agents

We study repeated implementation in a model with overlapping ge- nerations of agents. It is assumed that the preferences of agents do not change during their lifetime. A social choice function selects an alternative in each period as a function of the preferences of agents who are alive in that period. We show that any social choice function satisfying mild necessary conditions is repeatedly implementable in subgame perfect equilibrium if there are at least three agents and they live sufficiently long

Flat Tax Reform.The Baltics 2000 – 2007.

The paper presents an endogenous growth economy with a representation of the tax rate system in the Baltic countries. Assuming that government spending is a given fraction of output, the papershows how a flat tax system balanced between labor and corporate tax rates can be second best optimal. It then computes how actual Baltic tax reforms from 2000 to 2007 affect the growth rate and welfare, including transition dynamics. Comparing the actual reform effects to hypothetical tax experiments, it results that equal flat tax rates on personal and corporate income would have increased welfare in all three Baltic countries by 24% more on average than the actual reforms. This shows how equal, balanced, flat rate taxes can be optimal in both theory and practice. Further, movement towards a more equal balance between labor and capital tax rates, through changing just one tax rate, achieved almost as high or higher utility gains as in actual law for all three countries under both open and closed economy cases. This shows benefits of moving towards the optimum.tax reform, endogenous growth, transitional dynamics, flat taxes

Incumbency and Entry in License Auctions: The Anglo-Dutch Auction Meets Other Simple Alternatives

The existence of ex-ante strong incumbents may constitute a barrier to entry in auctions for goods such as licenses. Introducing inefficiencies that favor entrants is a way to induce entry and thus create competition. Designs such as the Anglo-Dutch auction have been proposed with this goal in mind. We first show that indeed the Anglo- Dutch auction fosters entry and increases the revenues of the seller. However, we argue that a more eective way could be to stage the allocation of the good so that each stage reveals information about the participants. We show that a sequence of English auctions, with high reserve prices in early rounds, is a procedure with this property that is more efficient than any one-stage entry auction. Moreover, it also dominates the Anglo-Dutch auction in terms of seller's revenues

Collusive communication schemes in a first-price auction

We study optimal bidder collusion at first-price auctions when the collusive mechanism only relies on signals about bidders' valuations. We build on Fang and Morris (2006) when two bidders have low or high private valuation of a single object and additionally each receives a private noisy signal from an incentiveless center about the opponent's valuation. We derive the unique symmetric equilibrium of the first price auction for any symmetric, possibly correlated, distribution of signals, when these can only take two values. Next, we find the distribution of 2-valued signals, which maximizes the joint payoffs of bidders. We prove that allowing signals to take more than two values will not increase bidders' payoffs if the signals are restricted to be public. We also investigate the case when the signals are chosen conditionally independently and identically out of n = 2 possible values. We demonstrate that bidders are strictly better off as signals can take on more and more possible values. Finally, we look at another special case of the correlated signals, namely, when these are independent of the bidders' valuations. We show that in any symmetric 2-valued strategy correlated equilibrium, the bidders bid as if there were no signals at all and, hence, are not able to collude

Taxation and the sustainability of collusion: ad valorem versus specific taxes

Assuming constant marginal cost, it is shown that a switch from specific to ad valorem taxation that results in the same collusive price has no effect on the critical discount factor required to sustain collusion. This result is shown to hold for Cournot oligopoly when collusion is sustained with Nash-reversion strategies or optimal-punishment strategies. In a Cournot duopoly model with linear demand and quadratic costs, it is shown that the critical discount factor is lower with an ad valorem tax than with a specific tax that results in the same collusive price. However, in contrast to Colombo and Labrecciosa (2013) it is shown that the revenue is always higher with an ad valorem tax than with a specific tax

A detail-free mediator

We present an extension to any finite complete information game with two players. In the extension, players are allowed to communicate directly and, additionally, send private messages to a simple, detail-free mediator, which, in turn, makes public announcements as a deterministic function of the private messages. The extension captures situations in which people engage in face-to-face communication and can observe the opponent's face during the conversation before choosing actions in some underlying game. We prove that the set of Nash equilibrium payoffs of the extended game approximately coincides with the set of correlated equilibrium payoffs of any underlying game

Collusive communication schemes in a first-price auction

We study optimal bidder collusion at first-price auctions when the collusive mechanism only relies on signals about bidders' valuations. We build on Fang and Morris (2006) when two bidders have low or high private valuation of a single object and additionally each receives a private noisy signal from an incentiveless center about the opponent's valuation. We derive the unique symmetric equilibrium of the first price auction for any symmetric, possibly correlated, distribution of signals, when these can only take two values. Next, we find the distribution of 2-valued signals, which maximizes the joint payoffs of bidders. We prove that allowing signals to take more than two values will not increase bidders' payoffs if the signals are restricted to be public. We also investigate the case when the signals are chosen conditionally independently and identically out of n > 2 possible values. We demonstrate that bidders are strictly better o¤ as signals can take on more and more possible values. Finally, we look at another special case of the correlated signals, namely, when these are independent of the bidders' valuations. We show that in any symmetric 2-valued strategy correlated equilibrium, the bidders bid as if there were no signals at all and, hence, are not able to collude

Taxation and the Sustainability of Collusion: Ad Valorem versus Specific Taxes

Assuming constant marginal cost, it is shown that a switch from specific to ad valorem taxation has no effect on the critical discount factor required to sustain collusion. This result is shown to hold for Cournot oligopoly as well as for Bertrand oligopoly when collusion is sustained with Nash-reversion strategies or optimal-punishment strategies. In a Cournot duopoly model with linear demand and quadratic costs, it is shown that the critical discount factor is lower with an ad valorem tax than with a specific tax. However, in contrast to Colombo and Labrecciosa (2013), it is shown that revenue is always higher with an ad valorem tax than with a specific tax

The optimality of optimal punishments in Cournot supergames

The result of Colombo and Labrecciosa (2006) that optimal punishments are inferior to Nash-reversion trigger strategies with decreasing marginal costs is due to the output when a firm deviates from the punishment path being allowed to become negative