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

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

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.Belgium; Effects; Income taxes; Personal;

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.

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.