The topological approach to the aggregation of preferences

(1) A domain of preferences allows for topological aggregation for each number of people if and only if this domain of preferences is contractible. (2) The combination of continuity and the Pareto principle implies the existence of a unique manipulator. (3) Arrow’s theorem can be translated into the previous statement. All of these results are obtained via algebraic topology. This paper introduces some of the tools developed in topology and applies them upon the problem of preference aggregation. This paper is based upon a lecture given at the conference “Mathematical aspects of social choice”, CREM, Université de Caen and CNRS, November 8–10, 2004. I thank the organizers Maurice Salles and Vincent Merlin for their warm hospitality, and the participants for the stimulating discussion. I am indebted to Bart Capéau and Roeland Vervenne for helpful remarks. I thank the referee for combining speed and quality.     

Feeling Attached and Feeling Accepted: Implications for Political Inclusion among Visible Minority Immigrants in Canada

Immigrants’ sense of belonging to their host communities is viewed as a core condition for their successful inclusion, but there is no consensus on which attributes of belonging are most relevant to understanding inclusion, nor is there agreement on how the sense of belonging ought to be measured empirically. This study examines how two related but independent dimensions of belonging help to better understand the political inclusion of visible minority immigrants in Canada. More specifically, it examines the role of feeling attached (immigrants’ feeling toward the host community) and the role of feeling accepted (immigrants’ sense of how their host communities feel about them). We assess the relationship between attachment, acceptance and political inclusion for both first- and second-generation visible minority Canadians; the results suggest there is analytical value in utilising separate measures of attachment and acceptance: political inclusion is more likely when both are stronger.     

A New Approach to Volatility Modeling: The Factorial Hidden Markov Volatility Model

A new process—the factorial hidden Markov volatility (FHMV) model—is proposed to model financial returns or realized variances. Its dynamics are driven by a latent volatility process specified as a product of three components: a Markov chain controlling volatility persistence, an independent discrete process capable of generating jumps in the volatility, and a predictable (data-driven) process capturing the leverage effect. An economic interpretation is attached to each one of these components. Moreover, the Markov chain and jump components allow volatility to switch abruptly between thousands of states, and the transition matrix of the model is structured to generate a high degree of volatility persistence. An empirical study on six financial time series shows that the FHMV process compares favorably to state-of-the-art volatility models in terms of in-sample fit and out-of-sample forecasting performance over time horizons ranging from 1 to 100 days. Supplementary materials for this article are available online.     

Dispersal-related traits of the snail Cornu aspersum along an urbanisation gradient: maintenance of mobility across life stages despite high costs

Urban Ecosystems - The extreme fragmentation of natural habitats due to urbanisation can influence the evolution of dispersal strategies in species persisting in cities. The brown garden snail...     

On simulation and properties of the stable law

The stable distribution, in its many parametrizations, is central to many stochastic processes. Many random variables that occur in the study of Lévy processes are related to it. Good progress has been made recently for simulating various quantities related to the stable law. In this note, we survey exact random variate generators for these distributions. Many distributional identities are also reviewed.     

Topological aggregation, the case of an infinite population

 The literature on infinite Chichilnisky rules considers two forms of anonymity: a weak and a strong. This note introduces a third form: bounded anonymity. It allows us to prove an infinite analogue of the “Chichilnisky– Heal-resolution” close to the original theorem: a compact parafinite CW-complex X admits a bounded anonymous infinite rule if and only if X is contractible. Furthermore, bounded anonymity is shown to be compatible with the finite and the [0, 1]-continuum version of anonymity and allows the construction of convex means in infinite populations. With X=[0, 1], the set of linear bounded anonymous rules coincides with the set of medial limits. Received: 30 October 1993/Accepted: 22 April 1996     

The Balinski–Young Comparison of Divisor Methods is Transitive

The ‘favoring small states’ relation of Balinski and Young (Fair representation, 1982) imposes stronger requirements on the nature of seat transfers than the majorization-ordering introduced by Marshall et al. (Soc Choice Welfare 19(4):885–900, 2002). For divisor methods, however, the two relations coincide. As a consequence, when restricted to the class of divisor methods the Balinski and Young relation is transitive.     

Positioning and role of public relations in large Belgian organizations

This paper studies the position and role of public relations in the hierarchical structure of Belgian organizations of at least 50 employees. Empirical data was collected from a web survey (n = 750) to find out to what extent principles of excellence in public relations are applied in Belgium.