Discussion of “On simulation and properties of the stable law” by L. Devroye and L. James

We contribute to the discussion of the paper by Devroye and James, by reviewing some of the most meaningful results that relate the unilateral stable distribution with the asymptotic behavior of the so-called Ewens-Pitman sampling model. Our focus is then on how these results have been exploited in the context of Bayesian nonparametric inference for species sampling problems.     

Diversity as width

It is argued that if a finite partially ordered population is given, and incomparability is taken as the relevant type of dissimilarity, then diversity comparisons between subpopulations may be conveniently based on widths namely on the maximum number of pairwise incomparable units they include. We introduce two width-based rankings. The first one is the plain width-ranking of subposets as induced by width computation. The second one is the undominated width-ranking of subposets namely the ranking induced by the sizes of undominated subposets. Simple axiomatic characterizations of the foregoing rankings are provided.     

After the End of History

Over the last century, the national approach has been the mainstream conception leading superpowers’ foreign policy, while the end of the Cold War brought about the worldwide multiplication of local conflicts. This differs from the past as this extensive international fragmentation urgently requires the adaptation of a new theoretical model to current international relations. This implies the re-consideration of some basic concepts such as national sovereignty, whose traditional fixed borders tend now to blur with a set of overlapping clusters of jurisdictional, economic, political, cultural interests.     

Purchasing performance management systems: an empirical investigation

This article aims at further developing the purchasing performance management systems (PPMSs) body of knowledge, assuming the wider perspective of the adoption process rather than key performance indicators (KPIs) only. In particular, the research questions are focused on understanding what are the most adopted indicators, what are the key elements characterising the implementation process and what are the differences among different organisational levels and different purchasing categories. The literature provides a framework for classifying purchasing KPIs, identifying the implementation process and the PPMS architecture, thus supporting the empirical research protocol. Nine case studies of large multinationals belonging to different industries are conducted. Empirical evidence shows that companies are still adopting mainly an external perspective, by focusing on performance measurement efforts on suppliers. Widely adopted indicators mainly measure cost, time and quality. However, the purchasing department has acquired an important role within the organisation and new performance indicators have been created; flexibility, innovation and sustainability are becoming increasingly important.     

Using Electronic Contact to Reduce Homonegative Attitudes,Emotions, and Behavioral Intentions Among Heterosexual Women and Men: A Contemporary Extension of the Contact Hypothesis

The current study experimentally examined the potential for a contemporary extension of the contact hypothesis, known as electronic contact, or E-contact, to reduce sexual prejudice, intergroup anxiety, and avoidant behavioral intentions among heterosexuals. It also extended the sexual minority contact literature by examining the role of participant and interaction partner sex as a possible boundary condition of this contact–prejudice relationship. To test our hypotheses, 140 heterosexual female and male university students were randomly allocated to interact with a homosexual or heterosexual, female or male E-contact partner, in a collaborative and text-only online interaction before completing the outcome measures. Overall, the results demonstrated that interacting online with a female, as opposed to a male, homosexual E-contact partner reduced heterosexual men’s feelings of intergroup anxiety, which in turn was associated with lower sexual prejudice and outgroup avoidance. For heterosexual women, however, E-contact did not influence the outcome variables. In the context of sexual prejudice, these results suggest that E-contact may be particularly useful as a prejudice-reduction strategy among individuals who typically require it most: heterosexual men.     

Recoverable robust timetabling for single delay: Complexity and polynomial algorithms for special cases

In this paper, we study the problem of planning a timetable for passenger trains considering that possible delays might occur due to unpredictable circumstances. If a delay occurs, a timetable could not be able to manage it unless some extra time has been scheduled in advance. Delays might be managed in several ways and the usual objective function considered for such purpose is the minimization of the overall waiting time caused to passengers. We analyze the timetable planning problem in terms of the recoverable robustness model, where a timetable is said to be recoverable robust if it is able to absorb small delays by possibly applying given limited recovery capabilities. The quality of a robust timetable is measured by the price of robustness that is the ratio between the cost of the recoverable robust timetable and that of a non-robust optimal one.     

Sub-Optimal Acquisition Decisions under a Majority Shareholder System

The high separation of ownership from control achieved through the concurrent use of non-voting shares and stock pyramiding could favor acquisitions made to increase private benefits of the controlling shareholders rather than all shareholders wealth. A standard event study methodology is carried out on three different samples of Italian acquisitions during the 1989–1996 period in order to test this hypothesis. We find evidence that a worse market reaction characterizes acquiring firms with a higher separation of ownership from control, while more value-enhancing transactions are undertaken by those smaller in size and with higher prior-performance. An entrenchment effect seems to determine a significant U-shaped relationship between the market reaction and the ultimate shareholder ownership. When the sample is restricted to acquiring firms with a dual class equity structure we find that non-voting shares report significantly negative excess returns in contrast to significantly higher positive returns for voting shares. Such evidence seems to indicate that the average acquisition has been overpaid, as suggested by the negative market reaction of the non-voting shares, while it was expected to lead to higher private benefits to the majority shareholders, as suggested by the revaluation of the voting shares. Finally, the market reaction to acquisitions made within pyramidal groups seems to indicate that the price is set so as to transfer wealth towards the companies located at the upper levels, where majority shareholders own greater fractions of the companies cash flows.JEL Codes: G34, G14A previous version of this paper was presented at the 1999 EFMA Conference in Paris, 1999 EFA Conference in Helsinki, and 1999 Australasian Banking and Finance Conference in Sydney. We would like to thank for helpful comments and suggestions, in alphabetical order: Lorenzo Caprio, Mara Faccio, Katiuscia Manzoni, Giovanni Siciliano, Sandro Sandri, the two anonymous referees and the editor. We would also like to thank Mara Faccio for providing ownership data. All remaining errors are ours.     

Estimating unobservable signal by Markovian noise induction

A sub threshold signal is transmitted through a channel and may be detected when some noise - with known structure and proportional to some level - is added to the data. There is an optimal noise level, called of stochastic resonance, that corresponds to the minimum variance of the estimators in the problem of recovering unobservable signals. For several noise structures it has been shown the evidence of stochastic resonance effect. Here we study the case when the noise is a Markovian process. We propose consistent estimators of the sub threshold signal and we solve further a problem of hypotheses testing. We also discuss evidence of stochastic resonance for both estimation and hypotheses testing problems via examples.