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PhD Defence: Maïmouna Diakite

Published on December 11, 2020 Updated on December 13, 2020
Le 14 December 2020 De 10:00 à 12:00

Efficacité et harmonisation des politiques fiscales : Cas de la zone UEMOA


Jean-François Brun, Associate Professor, Université Clermont Auvergne
Oliver Morrissey, Professor, Université de Nottingham
Fouzi Mourji, Professor, Université Hassan II
Sonia Schwartz, Professor, Université Clermont Auvergne


One of the main objectives of the West African Economic and Monetary Union (WAEMU) is the effective harmonization of the tax legislations of the member states. In accordance with the Decisions of the Council of Ministers of the WAEMU countries, the Commission of the WAEMU issued Directives to coordinate taxation in the Union. The implementation of these community acts by countries through tax reforms may affect their tax performance.

The purpose of this thesis is to identify the strengths of these community acts, assessing the inconsistencies, identifying the distortions that may result from their implementation, and how these factors affect the revenue mobilization in the WAEMU member states. We proceed by conducting a qualitative analysis of the community tax legislation. Then, we use empirical tools to measure the WAEMU member states’ tax performance for the different types of taxes and the total tax. Notably, Chapter 2 assesses independently the total tax effort, the non-resource tax effort and the value-added tax effort for a large sample of developing countries, including WAEMU member states, in using a robust methodology. Our results show that developing countries, especially low-income countries, make a significant effort to collect taxes. In particular, we observe that the tax effort indices of the WAEMU countries, especially the VAT effort indices, are substantial compared with those of the member states of other African Regional Economic Communities and the remaining ECOWAS countries. Chapter 3 evaluates the impact of the Directives, both in terms of coordination and revenue mobilization. It consists of a comparative case study using the synthetic control method. The main results are that the tax coordination has a positive impact on the revenue mobilization in the Union, especially for the indirect tax. However, the effect is different across countries and insignificant for the direct tax. Finally, Chapter 4 estimates the VAT gaps for all the WAEMU member states which have adopted VAT. Our calculations show substantial VAT gaps, for the WAEMU countries, which are mainly due to policy imperfections. We also conduct an econometric analysis to explain the impacts of vulnerability to illicit financial flows (IFFs) and digitalization on the estimated VAT gaps. We find that the vulnerability to IFFs through import has a significant and positive impact on the VAT gap, especially the Policy gap. As regards digitalization, we find that leads to a reduction of the Compliance Gap.


WAEMU, Tax, Tax potential, Tax effort, Value-added tax, Non-resource tax, Stochastic frontier analysis, Inefficiency, Tax coordination/harmonization, Tax reform, Synthetic control model, 2SLS-IV model, VAT gap, Policy gap, Compliance gap, Exemption gap, Rate gap, Illicit Financial Flows, Tax evasion, Tax fraud, Tax avoidance, Digitalization.