PhD Defences

Wouter Dister

• Wednesday 15 November 2023 - 5.00 p.m.
• Supervisors: prof. dr. Anne Van de Vijver (University of Antwerp) & prof. dr. Miet Vanderhallen (University of Antwerp and Maastricht University)
  
• Title: The Belgian Co-operative Tax Compliance Pilot ProjectKey Succes Indicators
• Abstract

Dieter Brughmans

• Friday 8 September 2023 4.00 p.m.
• Supervisors: David Martens & Bruno Peeters
• Title: Counterfactual explanations for real-world applications​
  

Abstract:

We first introduce NICE, a novel algorithm for tabular data that specifically takes into account algorithmic requirements that are often overlooked. NICE exploits information from the training data to speed up the search process of finding an explanation. Our extensive benchmarking study indicates that NICE’s explanations have desirable properties compared to the current state-of-the-art. Next, we study the implementation of NICE within the risk management system at the Belgian Customs Agency. Our research identified four stakeholders: data scientists, targeting officers, domain experts, and decision subjects. For each of the stakeholders, we investigate how they can benefit from local explanationmethods and what their requirements are regarding the form of these explanations. Broadening the scope of our research beyond tabular data, we introduce SEDC and SEDC-T, two counterfactual algorithms for image classification. We experiment with various segmentation methods to find meaningful counterfactual explanations. Finally, this work tackles the ethical issue of disagreement among counterfactual explanations, revealing how their diversity can potentially be exploited to fairwash ML models by hiding sensitive features. Our study finds alarmingly high disagreement levels between the tested methods.

Pedro Moraya Barros

• Monday 11 September 2023
• Supervisors: Ann Jorissen & Anne Van de Vijver
• Title: International Personal Taxation and Country Characteristics​
  

Abstract:

The increase in capital mobility in the last couple of decades, along with the rise in popularity of offshore investments, tax havens, and foreign taxation strategies, gave prominence to the importance of international taxation in domestic politics. Although income taxation often represents more than half of states’ revenue and has been positively correlated with economic development, 51 fiscally sovereign jurisdictions (which represent about 25% of the countries, 15% of the FDI, and 5% of the GDP of the world) chose to not tax their residents in foreign and/or domestic source income. The large divergence between personal income tax systems that exist today leads significant amounts of capital to flow from high to low tax jurisdictions, while potentially increasing wealth inequality. Thus, what are the country's characteristics related to the choice of personal income tax and related policies? To contribute to the answer to this question, I develop a 3-article dissertation divided between: (Chapter 2) What are the characteristics related to a country (not) having personal income taxation? (Chapter 3) What are the characteristics related to a country taxing residents on domestic-source income and not on foreign-source (i.e. personal territorial taxation)? (Chapter 4) What are the characteristics related to a country having policies potentially used by individuals to avoid or evade tax duties, i.e. the official selling of passports and visas? To test the theoretical models underlining these relationships based on Institutional Theory, Median Voter Theorem, Modernization Theory, and Bellicist Theories, I created several novel datasets that cover all sovereign jurisdictions in the world often through a long time series. Using these datasets, I employ a series of quantitative methods (e.g. ordinary least squares, maximum likelihood estimations, event analysis, error correction models, and instrumental variable approaches) that find significant empirical results for the fields of personal taxation, institutions, and foreign investment. This dissertation also has implications for broader questions in the literature.