Clinical and economic impact of rivaroxaban on the burden of atrial fibrillation: The case study of Japan

Objectives: Atrial fibrillation (AF) affects an estimated 1.5 million individuals in Japan, increasing their stroke risk and imposing considerable costs on the Japanese healthcare system. To reduce stroke incidence, guidelines recommend using anticoagulants in moderate-to-high risk non-valvular AF (NVAF) patients; however, many patients receive no treatment, aspirin only, or remain poorly-controlled on vitamin K antagonists (VKAs) due to high VKA discontinuation rates and non-adherence to guidelines. A prevalence-based Markov model was developed to estimate the clinical and budgetary impact of treating these patients with Xarelto^TM (rivaroxaban, Bayer AG) in Japan.

Methods: Population, baseline risk of events, and associated management costs were estimated using data from Japanese publications where available. Treatment efficacy and safety were derived from published data and the J-ROCKET AF trial. Drug and physician visit costs were based on data from the Ministry of Health, Labor, and Welfare, the J-ROCKET AF trial, and Japanese clinical guidelines.

Results: This model demonstrates that increased use of rivaroxaban in inadequately-managed NVAF patients could avoid 456 081 non-fatal ischemic strokes (IS) and 76 975 cardiovascular deaths over 10 years in Japan. This clinical benefit offsets the increased incidence of myocardial infarctions and anticoagulant-related bleeding. Decreased event costs could lead to a ¥188.4 billion decrease in net spending over the analysis time horizon.

Conclusions: Introducing rivaroxaban may decrease the burden of NVAF in Japanese society. From a clinical perspective, the reduction in IS and embolic events outweighs the increased risk of anticoagulant-related bleeding; from an economic perspective, reduced event costs offset drug and physician visit costs, resulting in cost savings.     

Team Roles and Hierarchic System in Group Discussion

Conventional systems for classifying team roles refer only to the function criterion and two categories, task and social; in addition, roles and behaviors are unspecialized, a one-to-one correspondence being assumed between them. These theoretical problems have resulted in overly fragmented roles as well as oversimplified categories. Therefore, this article aims to reveal essential roles and a unified system to classify them. In order to elucidate the team roles essential for discussion, a questionnaire survey was administered for Study 1, with the result that just ten discussant-roles were identified. For Study 2, in order to verify a classification system for the discussant-roles, participant groups were asked to discuss itineraries for an overnight group trip during the winter holiday. The results showed that a three-criterion model based on the deep roles is superior to the traditional model. In this hierarchical system, characteristic behaviors are expressed according to ten discussant-roles, which are divided into six categories, using a combination of three criteria. This system not only solves the theoretical issues but also contributes to improving members’ discussion behaviors.     

A dynamic analysis of collusive networks

This paper investigates the strategic formation of collusive networks in a dynamic framework. A collusive network is a set of market sharing agreements between firms in oligopolistic markets and auctions. Belleflamme and Bloch (Int Econ Rev 45(2):387–411, 2004) fully characterize the pairwise stable collusive networks in their symmetric model. In contrast, we characterize the collusive networks to which a dynamic network formation process converges with positive probability in the symmetric model. We provide a complete characterization for the case of the process that starts from a network with sufficiently few links. Moreover, we show that the process never cycles but always converges to a stable network. In addition, we discuss an asymmetric model where firms enjoy a home country advantage. We show that the expected number of collusive agreements may be reduced by an increase in the degree of the home country advantage. This implies that policies for discouraging entry may fail, and may lead to a decrease in expected social surplus.     

Productive Government Expenditures and the Current Account

This paper examines the effects of a change in government expenditure on the current account of the balance of payments using the optimizing approach. It is assumed that government expenditure is productive, and is regarded as an input in the aggregate production function. Based on the Blanchard–Fischer-type model, the paper demonstrates decisively that the current account deficit is due to a permanent increase in government expenditure.
JEL Classification Numbers: F41, H30.     

Web usage mining approaches to page recommendation and restructuring

As an increasing number of Web sites such as e-businesses consist of an increasing number of pages, users find it more difficult to rapidly reach their own target pages. Ill-structured design of Web sites also prevents the users from rapidly accessing the target pages. In this paper, we describe two complementary approaches to Web usage mining as a key solution to these issues. First, we describe an adaptable recommendation system called the L-R system, which constructs user models by classifying the Web access logs and by extracting access patterns based on the transition probability of page accesses and recommends the relevant pages to the users based on both the user models and the Web structures. We have evaluated the prototype system and have obtained the positive effects. Second, we describe another approach to constructing user models, which clusters Web access logs based on access patterns. The user models also help to discover unexpected access paths corresponding to ill-formed Web site design. Copyright © 2003 John Wiley & Sons, Ltd.     

The Japanese stock market and the macroeconomy: An empirical investigation

We investigate the relationship between macroeconomic variables, such as the industrial production index, interest rate and inflation rate, and the stock market, using Toda and Yamamoto (1995)'s vector autoregressions (VAR) specification. The major findings are: (1) macroeconomic variables do Granger cause the stock market variable, while reverse is not so clear. (2) The lagged stock market variable affects its current value but its impact tend to diminish in the long-run. Policy implication we draw is that the price keeping operation by the Japanese government would not work, but appropriate macroeconomic policies would benefit not only the real market but also the stock market.     

School Choice with General Constraints: A Market Design Approach for the Nursery School Waiting List Problem in Japan

This study considers a school choice problem with general feasibility constraints. Each student belongs to a grade; and 2 students belonging to the same grade are symmetric, whereas those belonging to different grades can be asymmetric with respect to the feasibility constraint of a school. We introduce five requirements of a matching and a polynomial‐time algorithm to derive a matching satisfying them. Because the algorithm is inspired by the nursery school system of Yokohama City, we introduce the system and compare it with the algorithm of this study.     

Axiomatization of the core of assignment games

The core of assignment games is characterized by two different lists of axioms. The first list consists of Pareto optimality, consistency, pairwise monotonicity, and individual monotonicity. The second list is obtained from the first one replacing the last axiom by population monotonicity. As a corollary, individual monotonicity and population monotonicity are equivalent under the other axioms. The core is also characterized by the second list on the restricted domain in which the worth of each pair is non-negative and every reservation value is zero.     

A Portfolio Index GARCH model

This paper develops the structure of a parsimonious Portfolio Index (PI) GARCH model. Unlike the conventional approach to Portfolio Index returns, which employs the univariate ARCH class, the PI-GARCH approach incorporates the effects on individual assets, leading to a better understanding of portfolio risk management, and achieves greater accuracy in forecasting Value-at-Risk (VaR) thresholds. For various asymmetric GARCH models, a Portfolio Index Composite News Impact Surface (PI-CNIS) is developed to measure the effects of news on the conditional variances. The paper also investigates the finite sample properties of the PI-GARCH model. The empirical example shows that the asymmetric PI-GARCH-t model outperforms the GJR-t model and the filtered historical simulation with a t distribution in forecasting VaR thresholds.     

The structure of dynamic correlations in multivariate stochastic volatility models

This paper proposes two types of stochastic correlation structures for Multivariate Stochastic Volatility (MSV) models, namely the constant correlation (CC) MSV and dynamic correlation (DC) MSV models, from which the stochastic covariance structures can easily be obtained. Both structures can be used for purposes of determining optimal portfolio and risk management strategies through the use of correlation matrices, and for calculating Value-at-Risk (VaR) forecasts and optimal capital charges under the Basel Accord through the use of covariance matrices. A technique is developed to estimate the DC MSV model using the Markov Chain Monte Carlo (MCMC) procedure, and simulated data show that the estimation method works well. Various multivariate conditional volatility and MSV models are compared via simulation, including an evaluation of alternative VaR estimators. The DC MSV model is also estimated using three sets of empirical data, namely Nikkei 225 Index, Hang Seng Index and Straits Times Index returns, and significant dynamic correlations are found. The Dynamic Conditional Correlation (DCC) model is also estimated, and is found to be far less sensitive to the covariation in the shocks to the indexes. The correlation process for the DCC model also appears to have a unit root, and hence constant conditional correlations in the long run. In contrast, the estimates arising from the DC MSV model indicate that the dynamic correlation process is stationary.