Irrelevant natural extension for choice functions

We consider coherent choice functions under the recent axiomatisation proposed by De Bock and De Cooman that guarantees a representation in terms of binary preferences, and we discuss how to define conditioning in this framework. In a multivariate context, we propose a notion of marginalisation, and its inverse operation called weak (cylindrical) extension. We combine this with our definition of conditioning to define a notion of irrelevance, and we obtain the irrelevant natural extension in this framework: the least informative choice function that satisfies a given irrelevance assessment

Non-suicidal self-injury in Latin America

Background Non-Suicidal Self-Injury (NSSI) is defined as the intentional direct injury of the own bodily tissue without suicidal intent. In areas with a Caucasian majority population, such as the USA, Canada and Europe, it is a rapidly increasing phenomenon, especially among young people. However, from a European point of view, little scientific information is found on NSSI in Latin America. Method A study of English, Spanish and Portuguese literature on NSSI in Latin America was conducted using electronic search engines. During a ten-month period of field work in Belo Horizonte, Brasil, a systematic search was conducted of the international press, the popular local press, television broadcasts, Internet sites and blogs. Semi-structured elite interviews were conducted of academic professionals and practitioners. Spontaneous conversations on NSSI took place with local inhabitants. Results Three reasons for the authors' prior lack of success in finding publications on NSSI in Latin America could be distinguished: the gap between academic professionals, practitioners and inhabitant population, the language of the publications, and the existing confusion in terminology and research traditions regarding NSSI. Conclusion NSSI has a high prevalence in Latin America, which can be Compared to that of the northern hemisphere. Although there are some differences in the ways of engaging in NSSI and in its functions, there are also important similarities. Scientific information on,NSSI in Latin America remains difficult to find for researchers in other parts of the world. Therefore we advocate a consensus in terminology and suggest that all publications would provide English key words and would be included in international scientific databases to ensure a world-wide dissemination. An alternative is-the construction of one centralized global Latin American database for Spanish and Portuguese publications

Exchangeable choice functions

We investigate how to model exchangeability with choice functions. Exchangeability is a structural assessment on a sequence of uncertain variables. We show how such assessments are a special indifference assessment, and how that leads to a counterpart of de Finetti's Representation Theorem, both in a finite and a countable context

Modelling practical certainty and its link with classical propositional logic

We model practical certainty in the language of accept & reject statement-based uncertainty models. We present three different ways, each time using a different nature of assessment: we study coherent models following from (i) favourability assessments, (ii) acceptability assessments, and (iii) indifference assessments. We argue that a statement of favourability, when used with an appropriate background model, essentially boils down to stating a belief of practical certainty using acceptability assessments. We show that the corresponding models do not form an intersection structure, in contradistinction with the coherent models following from an indifferenc assessment. We construct embeddings of classical propositional logic into each of our models for practical certainty

The unit of analysis in microsimulation models for personal income taxes: Fiscal unit or household?.

Administrative data on personal income taxes and household budget surveys differ in at least one important respect: the definition of the unit of observation. The sociological concept of a household does not coincide with the administrative definition of a fiscal unit. We investigate whether the evaluation of a reform of income taxes is sensitive to this difference. The empirical results are obtained for a major reform of personal income taxes in Belgium in 1988. We use the technique of statistical matching to link the fiscal data of the Ministry of Finance with the household budget survey. We find that the characteristics of the tax system before and after the reform, such as liability progression and residual progression, are sensitive to the unit of observation and to the data set used. But this sensitivity evaporates at the level of the reform.

Redistributive Effects of the Shift from Personal Income Taxes to Indirect Taxes: Belgium 1988-1993.

Between 1988 and 1993 the Belgian personal income tax system and the indirect tax system have been reformed to a considerable extent. We use microsimulation models to investigate the impact of the reform on the liability progression and the redistributive effect of the combined tax system. The redistributive effect of personal income taxes decreased, notwithstanding an increase in liability progression. For indirect taxes, both the liability regressivity and the reverse redistributive effect have been enhanced. We use recently developped statistical tests to gauge the significance of the observed changes.