Mechanism design without transfers

Many allocation problems preclude the use of monetary transfers (e.g. kidney exchange programs, task allocation...). Achieving efficiency is cumbersome given this constraint. My dissertation analyzes several of these problems: student-to-school assignment, collusion in auctions without side payments, and finally a general allocation problem without transfers."School choice: the case for the Boston Mechanism". I study school assignment problems, focusing on two popular mechanisms: the Boston Mechanism (BM) and Deferred Acceptance (DA). The latter has already replaced the former in several cities. I argue that given how priorities are commonly constructed among students (e.g. walking-distance and sibling in school), the number of priority classes is much smaller than the number of students, and tie-breaking lotteries are needed. In this uncertainty context, approximated by assuming only one priority class, I show that BM outperforms DA according to several ex ante efficiency criteria. DA performs very poorly if all students share identical ordinal preferences over schools. Simulations show that these analytical results extend to more realistic cases. Finally, I suggest a simple modification to BM, which according to simulations protects naive (non-strategic) students while largely preserving its efficiency properties."Self-enforced collusion through comparative cheap talk in simultaneous auctions with entry". I study a self-enforced collusion mechanism in simultaneous auctions based on complete comparative cheap talk and endogenous entry. This paper analyzes more-than-two-bidder, symmetric-prior cases. Two results are proved: (1) as the number of objects grows large, a full comparative cheap talk equilibrium exists and it yields asymptotically fully efficient collusion and (2) there is always a partial comparative cheap talk equilibrium. All these results are supported by intuitive equilibria at the entry-decision stage. Numerical examples suggest that full comparative cheap talk equilibria are not uncommon even with few objects."Cardinal Bayesian allocation mechanisms without transfers". This study contributes to the solution of the optimal allocation mechanism problem with several indivisible objects and no transfers, under Bayesian incentive compatibility. The main and simple idea to solve the problem is that the allocation probability for one of the objects can be used as a numeraire that is used to "auction the other objects off".