Ever since the seminal work by Rothschild and Stiglitz (1976) on competitive insurance markets under adverse selection the equilibrium-non-existence problem has been one of the major puzzles in insurance economics. We extend the original analysis by considering firms which face capacity constraints, which might be due to limited capital. We show that under mild assumptions a pure strategy equil...

We extend Armstrong’s [1] result on exclusion in multi-dimensional screening models providing support for the view that the result holds true in a large class of models. We first relax some of the strong technical assumptions he imposed and provide alternative su cient conditions for exclusion not relying on any form of convexity. We then proceed to show that exclusion obtains generically. We i...

In a principal-agent model with hidden information and no monetary transfers, I establish the Veto-Power Principle: any incentive-compatible outcome can be implemented through veto-based delegation with an endogenously chosen default decision. This result demonstrates the exact nature of commitment powers required by the principal: (1) to design the default outcome and (2) to ensure that she ha...

We consider a principal-agent model with moral hazard where the agent’s knowledge about the performance measure is ambiguous and he is averse towards ambiguity. We show that the principal may optimally provide no incentives or contract only on a subset of all informative performance measures. That is, the Informativeness Principle does not hold in our model. These results stand in stark contras...

We consider a perfectly competitive ex ante economy with a continuum of agents and negligible asymmetric information. For such an economy we recast the basic classical results on the existence of Walrasian equilibrium, core equivalence, and the blocking size of coalitions. Moreover, we examine the incentive compatibility of the ex ante Pareto, core and Walrasian allocations. © 2007 Elsevier Inc...

We study the second-price offer feature of eBay auctions in which the seller has multiple units. Perhaps surprisingly, the opportunity to make second-chance offers can reduce seller profit. This happens if her marginal cost function is sufficiently steep. Hence, sellers should be wary about the possibility that buyers anticipate second-chance offers, and it may be advantageous for a seller to a...

This paper studies disclosure dynamics and its implications for stock returns. Because disclosure is costly, the firm may withhold information for some time even when information is favorable. In equilibrium, the firm adopts a regular time-pattern of disclosure. Breaking this regularity, by failing to issue a disclosure when expected, leads to a sharp drop in the stock price and to a period of ...

Many separable dynamic incentive problems have primal recursive formulations in which utility promises serve as state variables. We associate families of dual recursive problems with these by selectively dualizing constraints. We make transparent the connections between recursive primal and dual approaches, relate value iteration under each and give conditions for such value iteration to be con...

The revelation principle asserts that every outcome brought by a mechanism is realized by a truthful direct mechanism. The present paper investigates the regularity conditions of these two mechanisms in the continuous space of the agent’s type. It questions what regularity condition a general mechanism confers upon a direct mechanism through the revelation principle. By so doing, we elucidate t...

We study the consequences of indexing, i.e. commiting to invest in risky assets only via the market portfolio. We extend the canonical rational expectations model (Grossman and Stiglitz, 1980) to allow for multiple assets and endowment shocks, and show that indexing imposes a negative externality on other uninformed agents. More indexing makes informed trading on the market more profitable, whi...