Beyond tail median and conditional tail expectation: Extreme risk estimation using tail Lp-optimization

The conditional tail expectation (CTE) is an indicator of tail behavior that takes into account both the frequency and magnitude of a tail event. However, the asymptotic normality of its empirical estimator requires that the underlying distribution possess a finite variance; this can be a strong restriction in actuarial and financial applications. A valuable alternative is the median shortfall (MS), although it only gives information about the frequency of a tail event. We construct a class of tail L^p-medians encompassing the MS and CTE. For p in (1,2), a tail L^p-median depends on both the frequency and magnitude of tail events, and its empirical estimator is, within the range of the data, asymptotically normal under a condition weaker than a finite variance. We extrapolate this estimator and another technique to extreme levels using the heavy-tailed framework. The estimators are showcased on a simulation study and on real fire insurance data.     

Online Poker Tilt Scale (OPTS): creation and validation of a tilt assessment in a French population

Tilt in poker implies a deviation from an individual’s usual playing style, at a strategic, emotional and behavioural level. It is a specific characteristic of poker, which can affect all kinds of players with varying degrees of frequency. In addition, tilt could be a transitional form of pathological gambling behaviour and a gateway to addiction. The main objective of this research is therefore the design and validation of a measuring scale for tilt episode frequency in an online poker gamblers’ group. Twenty-one items based on the literature and interviews with 10 poker players were created. An online self-administered questionnaire was completed by 263 poker players to validate this scale. The mean age of the sample was 26.7 (SD = 4.45). The Online Poker Tilt Scale (OPTS) consists of 17 items and is the first validated tool for measuring the frequency of tilt episodes associated with online poker. It is composed of two factors: ‘emotional and behavioural tilt’ and ‘cognitive tilt’. Tilt seems to be an essential part of understanding online poker behaviour. This tool will enable researchers studying online poker addiction to perform research on the mechanisms and processes that lead to tilt and its consequences.     

Twinning Rates in Developed Countries: Trends and Explanations

The twinning rate has increased dramatically over the last four decades in developed countries. Two main factors account for this increase: delayed childbearing, as older women tend to have twins more frequently than younger ones, and the expansion of medically assisted reproduction (MAR), which carries an increased probability of multiple births. Using civil registration data, we estimate the share of the increase in twinning rates attributable to the rise in the age at childbearing and to MAR. The effect of MAR is estimated to be about three times as important as the effect of delayed childbearing. Negative health outcomes associated with multiple births and the cost of MAR have raised concerns. We find that in one‐quarter of developed countries with the relevant data, the twinning rate reached a plateau around the early 2000s and decreased thereafter. We examine the reasons for this reversal, in particular changes in MAR policies and practices.     

Intervention sociology: history and foundations

Our intention is to state the main characteristics of intervention sociology, from its origins, the beginnings of which can be situated in Frédéric Le Play's monographic work carried out 150 years ago, to its present forms. Rather seldom mentioned in sociological literature or if so in the course of a paragraph or in methodological appendixes, intervention sociology, although widely practised outside the academic field, today still lacks legibility and institutional recognition. By proposing a thorough reading of the main theories and conceptions developed during the past two centuries, our article aims at explaining, through the sociological prism, the fundamental concepts of intervention sociology.     

Does digitization lead to the homogenization of cultural content?

Using weekly music charts data in 10 countries over the period 1990–2015, we analyze whether digitization leads to a trend of homogenization of music content or conversely to a greater acoustic disparity. We split the digitization era in four periods that correspond to four new emblematic distribution models (Napster, iTunes, YouTube, Spotify). Our main result is that while acoustic diversity decreased during the iTunes and the YouTube periods, the period that begins with the introduction of audio streaming services, such as Spotify, represents a turning point and is marked by a significant increase in acoustic diversity.     

Inference in model-based cluster analysis

A new approach to cluster analysis has been introduced based on parsimonious geometric modelling of the within-group covariance matrices in a mixture of multivariate normal distributions, using hierarchical agglomeration and iterative relocation. It works well and is widely used via the MCLUST software available in S-PLUS and StatLib. However, it has several limitations: there is no assessment of the uncertainty about the classification, the partition can be suboptimal, parameter estimates are biased, the shape matrix has to be specified by the user, prior group probabilities are assumed to be equal, the method for choosing the number of groups is based on a crude approximation, and no formal way of choosing between the various possible models is included. Here, we propose a new approach which overcomes all these difficulties. It consists of exact Bayesian inference via Gibbs sampling, and the calculation of Bayes factors (for choosing the model and the number of groups) from the output using the Laplace–Metropolis estimator. It works well in several real and simulated examples.     

ECONOMIC SCIENCE AND POLITICAL INFLUENCE

When policymakers and private agents use models, the economists who design the model have an incentive to alter it in order to influence outcomes in a fashion consistent with their own preferences. I discuss some consequences of the existence of such ideological bias. In particular, I analyze the role of measurement infrastructures such as national statistical institutes, the extent to which intellectual competition between different schools of thought may lead to polarization of views over some parameters and at the same time to consensus over other parameters, and finally how the attempt to preserve influence can lead to degenerative research programs.     

Corporate communications managers in large firms: new challenges

The new organisational form of large corporations (horizontal organisation), is affecting the communications job. This corporate transformation leads to new challenges for the corporate communications manager and his team. On the one hand, he has to develop a fully integrated strategy which enables the different forms of communication to contribute to the success of the firm's mission (a common goal). On the other hand, he has to provide small business units, led by strong front-line managers, with professional services. The analysis of several companies will show that the position of the corporate communications department is subject to various pressures and that the development of the `communications function' is calling into question the corporate communications manager's `profession'.