Reputation and Turnover

We consider a repeated duopoly game where each firm privately chooses its investment in quality, and realized quality is a noisy indicator of the firm’s investment. We focus on dynamic reputation equilibria, whereby consumers ‘discipline’ a firm by switching to its rival in the case that the realized quality of its product is too low. This type of equilibrium is characterized by consumers’ tolerance level - the level of product quality below which consumers switch to the rival firm - and firms’ investment in quality. Given consumers’ tolerance level, we determine when a dynamic equilibrium that gives higher welfare than the static equilibrium exists. We also derive comparative statics properties, and characterize a set of investment levels and, hence, layoffs that our equilibria sustain.Reputation, consumer switching, moral hazard, repeated games

Optimal Sharing Rules in Repeated Partnerships

We study a simple model of repeated partnerships with noisy outcomes. Two partners first choose a sharing rule, under which they start their repeated interaction. We characterize the sharing rule which supports the most efficient equilibrium, and show that it suffices to consider two particular sharing rules. One is an asymmetric sharing rule, which induces only a more productive partner to work. It is optimal for impatient or less productive partners. The other treats them more evenly, and prevails for more productive and patient partners. Those results indicate how technological parameters and patience determine the role of a more productive partner. If the partners become more productive or more patient, the productive partner ceases to be a residual claimant and sacrifices his own share, in order to foster teamwork.

Repeated Multimarket Contact with Private Monitoring: A Belief-Free Approach

This paper studies repeated games where two players play multiple duopolistic games simultaneously (multimarket contact). A key assumption is that each player receives a noisy and private signal about the other's actions (private monitoring or observation errors). There has been no game-theoretic support that multimarket contact facilitates collusion or not, in the sense that more collusive equilibria in terms of per-market profits exist than those under a benchmark case of one market. An equilibrium candidate under the benchmark case is belief-free strategies. We are the first to construct a non-trivial class of strategies that exhibits the effect of multimarket contact from the perspectives of simplicity and mild punishment. Strategies must be simple because firms in a cartel must coordinate each other with no communication. Punishment must be mild to an extent that it does not hurt even the minimum required profits in the cartel. We thus focus on two-state automaton strategies such that the players are cooperative in at least one market even when he or she punishes a traitor. Furthermore, we identify an additional condition (partial indifference), under which the collusive equilibrium yields the optimal payoff.Comment: Accepted for the 9th Intl. Symp. on Algorithmic Game Theory; An extended version was accepted at the Thirty-Fourth AAAI Conference on Artificial Intelligence (AAAI-20

The folk theorem for repeated games with observation costs

This paper studies repeated games with private monitoring where players make optimal decisions with respect to costly monitoring activities, just as they do with respect to stage-game actions. We consider the case where each player can observe other players' current-period actions accurately only if he incurs a certain level of disutility. In every period, players decide whether to monitor other players and whom to monitor. We show that the folk theorem holds for any finite stage game that satisfies the standard full dimensionality condition and for any level of observation costs. The theorem also holds under general structures of costless private signals and does not require explicit communication among the players. Therefore, tacit collusion can attain efficient outcomes in general repeated games with private monitoring if perfect private monitoring is merely feasible, however costly it may be

地方自治体の高等教育施策に関する調査研究

日本教育社会学会第37回大会, 1985年10月(お茶の水大学), Ⅲ-2部会 高等教

Establishment of Functioning Human Corneal Endothelial Cell Line with High Growth Potential

Hexagonal-shaped human corneal endothelial cells (HCEC) form a monolayer by adhering tightly through their intercellular adhesion molecules. Located at the posterior corneal surface, they maintain corneal translucency by dehydrating the corneal stroma, mainly through the Na+- and K+-dependent ATPase (Na+/K+-ATPase). Because HCEC proliferative activity is low in vivo, once HCEC are damaged and their numbers decrease, the cornea begins to show opacity due to overhydration, resulting in loss of vision. HCEC cell cycle arrest occurs at the G1 phase and is partly regulated by cyclin-dependent kinase inhibitors (CKIs) in the Rb pathway (p16-CDK4/CyclinD1-pRb). In this study, we tried to activate proliferation of HCEC by inhibiting CKIs. Retroviral transduction was used to generate two new HCEC lines: transduced human corneal endothelial cell by human papillomavirus type E6/E7 (THCEC (E6/E7)) and transduced human corneal endothelial cell by Cdk4R24C/CyclinD1 (THCEH (Cyclin)). Reverse transcriptase polymerase chain reaction analysis of gene expression revealed little difference between THCEC (E6/E7), THCEH (Cyclin) and non-transduced HCEC, but cell cycle-related genes were up-regulated in THCEC (E6/E7) and THCEH (Cyclin). THCEH (Cyclin) expressed intercellular molecules including ZO-1 and N-cadherin and showed similar Na+/K+-ATPase pump function to HCEC, which was not demonstrated in THCEC (E6/E7). This study shows that HCEC cell cycle activation can be achieved by inhibiting CKIs even while maintaining critical pump function and morphology

Full Collusion with Entry and Incomplete Information

This paper studies an infinitely repeated duopoly game with incomplete information and with costly entry decisions. Every period, each player learns her private type and decides whether to pay a cost in order for her to enter or not. If she enters, she plays a game belonging to a class that includes Bertrand duopoly and some auction games as special cases, either as a monopolist or as a duopolist. The players can communicate before they make their entry decisions. We study full collusion (joint profit maximization) in this environment which requires a higher-quality player to solely enter and to choose an action maximizing the stage payoff. We present a condition on the stage game which is both necessary and sufficient in order for full collusion to be an equilibrium outcome for sufficiently patient players. The condition is more likely to hold when the entry cost increases, which signifies that the entry cost is an important factor facilitating full collusion. We also show that under some parameter restrictions, asymmetric equilibria where only one player reveals her type every period sustain full collusion for a wider range of discount factors. These asymmetric equilibria reduce the total amount of communication, which makes it harder for antitrust authorities to detect collusion