Efficiency in Matching Markets with Regional Caps: The Case of the Japan Residency Matching Program

In an attempt to increase the placement of medical residents to rural hospitals, the Japanese government recently introduced "regional caps" which restrict the total number of residents matched within each region of the country. The government modified the deferred acceptance mechanism incorporating the regional caps. This paper shows that the current mechanism may result in avoidable ineffciency and instability and proposes a better mechanism that improves upon it in terms of effciency and stability while meeting the regional caps. More broadly, the paper contributes to the general research agenda of matching and market design to address practical problems.medical residency matching, regional caps, the rural hospital theorem, sta- bility, strategy-proofness, matching with contracts

Phase Transitions in Twin Higgs Models

We study twin Higgs models at non-zero temperature and discuss cosmological phase transitions as well as their implications on electroweak baryogenesis and gravitational waves. It is shown that the expectation value of the Higgs field at the critical temperature of the electroweak phase transition is much smaller than the critical temperature, which indicates two important facts: (i) the electroweak phase transition cannot be analyzed perturbatively (ii) the electroweak baryogenesis is hardly realized in the typical realizations of twin Higgs models. We also analyze the phase transition associated with the global symmetry breaking, through which the Standard Model Higgs is identified with one of the pseudo-Nambu-Goldstone bosons in terms of its linear realization, with and without supersymmetry. For this phase transition, we show that, only in the supersymmetric case, there are still some parameter spaces, in which the perturbative approach is validated and the phase transition is the first order. We find that the stochastic gravitational wave background is generated through this first order phase transition, but it is impossible to be detected by DECIGO or BBO in the linear realization and the decoupling limit. The detection of stochastic gravitational wave background with the feature of first order phase transition, therefore, will give strong constraints on twin Higgs models.Comment: 33 pages, 5 figures; v2: journal versio

Contracting with Word-of-Mouth Management

We incorporate word of mouth (WoM) in a classic Maskin-Riley contracting problem, allowing for referral rewards to senders of WoM. Current customers’ incentives to engage in WoM can affect the contracting problem of a firm in the presence of positive externalities of users. We fully characterize the optimal contract scheme and provide comparative statics. In particular, we show that offering a free contract is optimal only if the fraction of premium users in the population is small. The reason is that by offering a free product, the firm can incentivize senders to talk by increasing expected externalities that they receive and this is effective only if there are many free users. This result is consistent with the observation that companies that successfully offer freemium contracts oftentimes have a high percentage of free users

Contracting with Word-of-Mouth Management

We incorporate word of mouth (WoM) in a classic Maskin-Riley contracting problem, allowing for referral rewards to senders of WoM. Current customers’ incentives to engage in WoM can affect the contracting problem of a firm in the presence of positive externalities of users. We fully characterize the optimal contract scheme and provide other comparative statics. In particular, we show that offering a free contract is optimal only if the fraction of premium users in the population is small. The reason is that by offering a free product, the firm can incentivize senders to talk by increasing expected externalities that they receive and this can (partly) substitute for paying referral rewards only if there are few premium customers. This result is consistent with the observation that companies that successfully offer freemium contracts oftentimes have a high percentage of free users

Essays in Revision Games

This dissertation consists of three essays related to revision games. The first essay proposes and analyzes a new model that we call “revision games,” which captures a situation where players in advance prepare their actions in a game. After the initial preparation, they have some opportunities to revise their actions, which arrive stochastically. Prepared actions are assumed to be mutually observable. We show that players can achieve a certain level of cooperation. The optimal behavior of players can be described by a simple differential equation. The second essay studies a version of revision games in which revision opportunities are asynchronous across players. In 2-player “common interest” games where there exists a best action profile for all players, this best action profile is the only equilibrium outcome of the revision game. In “opposing interest” games which are 2 x 2 games with Pareto-unranked strict Nash equilibria, the equilibrium outcome of the revision game is generically unique and corresponds to one of the stage-game Nash equilibria. Which equilibrium prevails depends on the payoff structure and on the relative frequency of the arrivals of revision opportunities for each of the players. The third essay studies a multi-agent search problem with a deadline: for instance, the situation that arises when a husband and a wife need to find an apartment by September 1. We provide an understanding of the factors that determine the positive search duration in reality. Specifically, we show that the expected search duration does not shrink to zero even in the limit as the search friction vanishes. Additionally, we find that the limit duration increases as more agents are involved, for two reasons: the ascending acceptability effect and the preference heterogeneity effect. The convergence speed is high, suggesting that the mere existence of some search friction is the main driving force of the positive duration in reality. Welfare implications and a number of discussions are provided. Results and proof techniques developed in the first two essays are useful in proving and understanding the results in the third essay.Economic

Legislative Committees as Information Intermediaries: A Unified Theory of Committee Selection and Amendment Rules

This paper considers a model of legislative decision-making, in which information must be collected from a strategic lobbyist. The legislature appoints a committee to communicate with the lobbyist and propose a bill, and determines whether the proposal is processed under open or closed rule. Consistent with empirical evidence, it can be optimal for the legislature to appoint a biased committee and, depending on the lobbyist\u27s bias, both open and closed rule are used in equilibrium. For small lobbyist bias, it is optimal to choose closed rule and a committee whose interests are perfectly aligned with the lobbyist\u27s. For intermediate lobbyist bias, closed rule remains optimal with a committee whose preferences lie between those of the legislature and those of the lobbyist. For large lobbyist bias, open rule and a committee biased against the lobbyist become optimal

Extreme Lobbyists and Policy Convergence

We consider a two-candidate election model with campaign contributions. In the first stage of the game, each of two candidates chooses a policy position. In the second stage, each of n lobbyists chooses the amount of contribution to each candidate. The winning probability of each candidate depends on the total amount of contributions that she raised from the lobbyists. In any equilibrium of our model, only extreme lobbyists contribute at any subgame, and the policies converge on the unique equilibrium path. Our results suggest that extreme lobbyists and their contributions do not necessarily cause policies to diverge.41 p

Guidelines for the use and interpretation of assays for monitoring autophagy (3rd edition)

In 2008 we published the first set of guidelines for standardizing research in autophagy. Since then, research on this topic has continued to accelerate, and many new scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Accordingly, it is important to update these guidelines for monitoring autophagy in different organisms. Various reviews have described the range of assays that have been used for this purpose. Nevertheless, there continues to be confusion regarding acceptable methods to measure autophagy, especially in multicellular eukaryotes. For example, a key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers or volume of autophagic elements (e.g., autophagosomes or autolysosomes) at any stage of the autophagic process versus those that measure fl ux through the autophagy pathway (i.e., the complete process including the amount and rate of cargo sequestered and degraded). In particular, a block in macroautophagy that results in autophagosome accumulation must be differentiated from stimuli that increase autophagic activity, defi ned as increased autophagy induction coupled with increased delivery to, and degradation within, lysosomes (inmost higher eukaryotes and some protists such as Dictyostelium ) or the vacuole (in plants and fungi). In other words, it is especially important that investigators new to the fi eld understand that the appearance of more autophagosomes does not necessarily equate with more autophagy. In fact, in many cases, autophagosomes accumulate because of a block in trafficking to lysosomes without a concomitant change in autophagosome biogenesis, whereas an increase in autolysosomes may reflect a reduction in degradative activity. It is worth emphasizing here that lysosomal digestion is a stage of autophagy and evaluating its competence is a crucial part of the evaluation of autophagic flux, or complete autophagy. Here, we present a set of guidelines for the selection and interpretation of methods for use by investigators who aim to examine macroautophagy and related processes, as well as for reviewers who need to provide realistic and reasonable critiques of papers that are focused on these processes. These guidelines are not meant to be a formulaic set of rules, because the appropriate assays depend in part on the question being asked and the system being used. In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to monitor autophagy. Along these lines, because of the potential for pleiotropic effects due to blocking autophagy through genetic manipulation it is imperative to delete or knock down more than one autophagy-related gene. In addition, some individual Atg proteins, or groups of proteins, are involved in other cellular pathways so not all Atg proteins can be used as a specific marker for an autophagic process. In these guidelines, we consider these various methods of assessing autophagy and what information can, or cannot, be obtained from them. Finally, by discussing the merits and limits of particular autophagy assays, we hope to encourage technical innovation in the field