The core-walras equivalence

The equivalence of cores and competitive equilibrium sets in the very general framework of Boolean rings and algebras is proved. The results include most previous results as special cases. In particular, it is shown that Theorems 1 and 2 of M. K. Richter (J. Econom. Theory3 (1971), 323–334) remain true without the usual assumptions of δ-algebras for coalitions and δ-additive measures for allocations. This permits economies with countably many agents, rather than requiring continuumly many.     

Probability and the subjective evidence condition

This article is an attempt to clarify and possibly extend Achinstein's idea of subjective evidence. The argument is made that even though the idea of subjective evidence is ambiguous in many respects, if clarified, it holds potentially important consequences for various branches of knowledge. An attempt is made to show how the concept of subjective evidence may be given a probabilistic interpretation. This is done by introducing the idea of a potentially relevant class of evidence statements.     

Modeling the contemporaneous duration dependence for high-frequency stock prices

This paper proposes a novel copula approach to model the contemporaneous duration dependence for high-frequency (HF) stock prices via the bivariate hazard function. This method is useful in understanding the mechanism through which the prices of financial assets jointly adjust to reflect new information. In the empirical analysis, we use the HF data on the APPLE and IBM stocks to illustrate the feasibility of our approach. In brief, the main findings are as follows: (1) there is a strong evidence of contemporaneous duration dependence between the prices of these stocks and (2) as a result the estimators of the bivariate hazard function are sensitive to the choice of copulas under our study.     

POWER UTILITY MAXIMIZATION IN CONSTRAINED EXPONENTIAL LÉVY MODELS

We study power utility maximization for exponential Lévy models with portfolio constraints, where utility is obtained from consumption and/or terminal wealth. For convex constraints, an explicit solution in terms of the Lévy triplet is constructed under minimal assumptions by solving the Bellman equation. We use a novel transformation of the model to avoid technical conditions. The consequences for q‐optimal martingale measures are discussed as well as extensions to nonconvex constraints.     

Employability enhancement through formal and informal learning: an empirical study among Dutch non‐academic university staff members

Although learning is generally perceived as a way to improve employees' current job performance, so far, no research has been conducted to explore the possible relationships between formal and informal learning, on the one hand, and employability, on the other. Though contemporary views stress the importance of the job as a powerful learning site, considerable research evidence underpinning these views is lacking. This paper goes into the impact of formal and informal learning upon employability. The influence of employee characteristics and organizational factors is also taken into account. An e‐questionnaire was used to collect data among 215 Dutch non‐academic university staff members. Our findings emphasize the necessity of Human Resource Development strategies that encompass a mix of formal and informal learning opportunities. In particular, participation in networks appears to be an important predictor for employability. With the outcomes of this study, we aim to contribute to the further development of theoretical insights regarding employability enhancement through learning possibilities embedded in the workplace. It seems that strategies that focus exclusively on enhancing informal on‐the‐job learning should not be encouraged. Our study is limited to one context and further research is required to investigate the generalizability of the findings to other occupations and/or countries.     

Why top management team characteristics matter when employing a chief operating officer: a strategic contingency perspective

Critics of the CEO/COO duo have stressed that this arrangement burdens the firm with increased costs and decreases the CEO's effectiveness. This study adopts an upper echelon perspective to argue that the presence of a COO may also create TMT‐level information‐processing benefits that can improve firm performance in certain conditions. Data from a sample of 153 firms in five industries highlight a strong positive relationship between the presence of a COO and two established measures of firm performance: return on assets and market‐to‐book ratio. The data also suggest that those relationships are contingent on the broader characteristics of the TMT. Copyright © 2009 John Wiley & Sons, Ltd.     

Using PDA consistency checks to increase the precision of profits and sales measurement in panels

Personalized Digital Assistants (PDAs) and other forms of hardware needed to collect survey data electronically have become more affordable and powerful in recent years, leading to their use in a number of surveys in developing countries. Simple use of these devices can offer the prospect of more timely data entry and greater accuracy in guiding respondents through skip patterns. Further benefits are possible through the use of more complex consistency checks. We use PDAs to measure sales and profits for microenterprises, which are notoriously noisy. Consistency checks in the cross-section compare sales and profits, while those in the panel query responses which result in large changes from one period to the next. Cross-sectional checks also served as a second prompt in the case of missing profits. These checks do succeed in reducing the standard deviation and in increasing the correlation of the observations for which corrections are made. However, we find that the vast majority of large changes in enterprise sales and profits are confirmed by firm owners as genuine, highlighting the volatility of income in this sector. As a result, the overall impact of these consistency checks on the full sample is rather limited, suggesting that while such checks are useful if computerized forms of data collection are being used, the consistency checks per se are not a strong reason for using computerized data collection in collecting firm profits and sales.