Sebastian Kranz

Infinitely repeated games with public monitoring and monetary transfers

This paper studies infinitely repeated games with imperfect public monitoring and the possibility of monetary transfers. It is shown that all public perfect equilibrium payoffs can be implemented with a simple class of stationary equilibria that use stick-and-carrot punishments. A fast algorithm is developed that exactly computes the set of pure strategies equilibrium payoffs for all discount factors.

Renegotiation-proof relational contracts

We study infinitely repeated two-player games with perfect monitoring and assume that each period consists of two stages: one in which the players simultaneously choose an action and one in which they can transfer money to each other. In the first part of the paper, we derive simple conditions that allow a constructive characterization of all Pareto-optimal subgame perfect payoffs for all discount factors. In the second part, we examine different concepts of renegotiation-proofness and extend the characterization to renegotiation-proof payoffs.

Discounted Stochastic Games with Voluntary Transfers

This paper studies discounted stochastic games perfect or imperfect public monitoring and the opportunity to conduct voluntary monetary transfers. We show that for all discount factors every public perfect equilibrium payoff can be implemented with a simple class of equilibria that have a stationary structure on the equilibrium path and optimal penal codes with a stick and carrot structure. We develop algorithms that exactly compute or approximate the set of equilibrium payoffs and find simple equilibria that implement these payoffs.

Using Forward Contracts to Reduce Regulatory Capture

A fully unbundled, regulated network firm of unknown efficiency level can undertake unobservable effort to increase the likelihood of low downstream prices, e.g., by facilitating downstream competition. To incentivize such effort, the regulator can use an incentive scheme paying transfers to the firm contingent on realized downstream prices. Alternatively, the regulator can propose to the firm to sell the following forward contracts: the firm pays the downstream price to the owners of a contract, but receives the expected value of the contracts when selling them to a competitive financial market. We compare the two regulatory tools with respect to regulatory capture: if the regulator can be bribed to suppress information on the underlying state of the world (the basic probability of high downstream prices, or the type of the firm), optimal regulation uses forward contracts only.

Predatory Short Sales and Bailouts

Abstract This paper extends the literature on predatory short selling and bailouts through a joint analysis of the two. We consider a model with informed short sales, as well as uninformed predatory short sales, which can trigger the inefficient liquidation of a firm. We obtain several novel results: A government commitment to bail out insolvent firms with positive probability can increase welfare because it selectively deters predatory short selling without hampering desirable informed short sales. Contrasting a common view, bailouts can be optimal ex ante but undesirable ex post. Furthermore, bailouts in our model are a better policy tool than short selling restrictions. Welfare gains from the bailout policy are unevenly distributed: shareholders gain while taxpayers lose. Bailout taxes allow ex ante Pareto improvements.

Reconciliating Relational Contracting and Hold-Up: A Model of Repeated Negotiations

We propose a unified framework to study relational contracting and hold-up problems in infinite horizon stochastic games with monetary transfers. Starting from the observation that the common formulation of relational contracts as Pareto-optimal public perfect equilibria is in stark contrast to fundamental assumptions of hold-up models, we develop a model in which relational contracts are repeatedly negotiated in a relationship. New negotiations take place with positive probability each period and treat previous informal agreements as bygones. The concept nests relational contracting and hold-up models as opposite corner cases. Allowing for intermediate cases sheds light on many plausible trade-offs that do not arise in these corner cases.

Using Forward Contracts to Reduce Regulatory Capture: Using Forward Contracts to Reduce Regulatory Capture

A fully unbundled, regulated network firm of unknown efficiency level can untertake unobservable effort to increase the likelihood of low downstream prices, e.g. by facilitating downstream competition. To incentivize such effort, the regulator can use an incentive scheme paying transfers to the firm contingent on realized downstream prices. Alternatively, the regulator can force the firm to sell the following forward contracts: the firm pays the downstream price to the owners of a contract, but recieves the expected value of the contracts when selling them to a competivitve financial market. We compare the two regulatory tools with respect to regulatory capture: if the regulator can be bribed to suppress information on the underlying state of the world (the basic propability of high downstream prices, or the type of the firm), optimal regulation uses forward contracts only.

Relational Contracting, Repeated Negotiations, and Hold-Up

We propose a unified framework to study relational contracting and hold-up problems in infinite horizon stochastic games. We first illustrate that with respect to long run decisions, the common formulation of relational contracts as Pareto-optimal public perfect equilibria is in stark contrast to fundamental assumptions of hold-up models. We develop a model in which relational contracts are repeatedly newly negotiated during relationships. Negotiations take place with positive probability and cause bygones to be bygones. Traditional relational contracting and hold-up formulations are nested as opposite corner cases. Allowing for intermediate cases yields very intuitive results and sheds light on many plausible trade-offs that do not arise in these corner cases. We establish a general existence result and a tractable characterization for stochastic games in which money can be transferred.

Social Planning with Partial Knowledge of Social Interactions. Comment

Charles Manskis article (Manski [2009]) addresses a fundamental question: how to make policy decisions under ambiguity, i.e., when objective probabilities are unknown. Specifically, the article asks how a social planner should assign a continuum of individuals to one of two treatments. Two cases are analyzed: one in which treatment effects are individual, and one in which there are social interactions, meaning that the treatment choice for one group affects the well-being of the other group. The article offers the following formal foundation for planning under ambiguity: The social planner has to (a) choose a social welfare function, (b) assess the feasible states of nature, (c) select a criterion for decision-making under ambiguity. The framework thus abstracts from problems of finding the welfare function or defining the possible states of the world, i.e., the article does not analyze cases in which the social planner does not even feel comfortable with writing down possible events and their consequences in a utilitarian manner. But even when (a) and (b) pose no problems, it is not yet clear what decision should be taken, because typically one decision is optimal in one state, while another is optimal in another state. In order to decide, the social planner must somehow give weights to the states, which he can do by assigning subjective probabilities. He can then rank the decisions according to the expected welfare they generate, which is the familiar Bayesian decision criterion.