En Tunisie, comme dans plusieurs pays méditerranéens, la céréaliculture est une activité très consommatrice de pesticides (63% de la consommation totale de l'agriculture tunisienne). Par conséquent, il est nécessaire d'étudier le devenir des pesticides appliqués afin de réduire les quantités perdues dans l'environnement tout en maintenant un niveau acceptable de l'efficacité des traitements. Plusieurs études ont montré qu'après leur éjection par la buse, les gouttelettes sont plus ou moins soumises aux phénomènes de dérive et de perte au sol pendant le traitement. La partie principale de ce travail est basée sur le développement et la validation d'un modèle capable de calculer les dépôts, la volatilisation (évaporation et pertes vers l'air) sous le vent, en grandes cultures. Le modèle DriftL, modèle de dérive à complexité réduite, a été alors construit sous le logiciel SciLab, version 5,03. Il a été paramétré à partir de mesures réalisées sous des conditions contrôlées en soufflerie et a bénéficié d'une validation expérimentale. Une deuxième partie étudie expérimentalement les pertes directes au sol et la rétention sur les plantes en conditions de laboratoire. Comme pour le travail mené en soufflerie, il a été possible de mettre en évidence une relation entre la granulométrie des gouttelettes, la hauteur des buses, les variables microclimatiques et les dépôts mesurés dans les compartiments air, sol et plante. Pour effectuer ces mesures, une démarche expérimentale a été mise en place afin de choisir la méthode de travail la mieux adaptée. Après de nombreux tests, un collecteur a été sélectionné pour chaque compartiment. Une rampe mobile a été également fabriquée pour jouer le rôle du pulvérisateur dans les conditions de laboratoire. Les mesures effectuées au champ ont permis de valider certains des calculs de DriftL ainsi que les résultats obtenus au laboratoire.

En Tunisie, comme dans plusieurs pays méditerranéens, la céréaliculture est une activité très consommatrice de pesticides (63% de la consommation totale de l'agriculture tunisienne). Par conséquent, il est nécessaire d'étudier le devenir des pesticides appliqués afin de réduire les quantités perdues dans l'environnement tout en maintenant un niveau acceptable de l'efficacité des traitements. Plusieurs études ont montré qu'après leur éjection par la buse, les gouttelettes sont plus ou moins soumises aux phénomènes de dérive et de perte au sol pendant le traitement. La partie principale de ce travail est basée sur le développement et la validation d'un modèle capable de calculer les dépôts, la volatilisation (évaporation et pertes vers l'air) sous le vent, en grandes cultures. Le modèle DriftL, modèle de dérive à complexité réduite, a été alors construit sous le logiciel SciLab, version 5,03. Il a été paramétré à partir de mesures réalisées sous des conditions contrôlées en soufflerie et a bénéficié d'une validation expérimentale. Une deuxième partie étudie expérimentalement les pertes directes au sol et la rétention sur les plantes en conditions de laboratoire. Comme pour le travail mené en soufflerie, il a été possible de mettre en évidence une relation entre la granulométrie des gouttelettes, la hauteur des buses, les variables microclimatiques et les dépôts mesurés dans les compartiments air, sol et plante. Pour effectuer ces mesures, une démarche expérimentale a été mise en place afin de choisir la méthode de travail la mieux adaptée. Après de nombreux tests, un collecteur a été sélectionné pour chaque compartiment. Une rampe mobile a été également fabriquée pour jouer le rôle du pulvérisateur dans les conditions de laboratoire. Les mesures effectuées au champ ont permis de valider certains des calculs de DriftL ainsi que les résultats obtenus au laboratoire.

Over the last few decades, production processes have become increasingly fragmented: they are divided into ever smaller parts considered as separate activities, which are then spread over various locations in different countries. In other words, value chains for many products are becoming global. This implies that inputs into the production process are sourced from both local and foreign suppliers. The latter mode of sourcing is commonly referred to as offshoring. Expressed as the share of imported in total intermediates, offshoring has grown relatively fast in the recent past. Moreover, its scope has been extended as it increasingly encompasses not only manufacturing but also service activities. A typical example for the former is the sourcing from abroad of parts and components for car assembly. While offshoring of manufacturing activities has been occurring since long and has been largely facilitated by trade liberalisation, the offshoring of service activities such as the provision of accounting or call centre services is a more recent phenomenon that has been fostered by the increased tradability of such services.<p>With the increasing scale and scope of offshoring, it becomes crucial to get a grasp of its drivers as well as the gains and threats associated with it. The latter are the focal point of the public and academic discussion around offshoring, in particular the potential threats for workers in developed economies. Typical questions that are being raised are whether offshoring leads to job losses in developed countries and whether it favours certain categories of workers and is to the disadvantage of others. These threats are directly linked to the motivations for engaging into offshoring. In this respect, wage costs play a prominent role. But other factors may also influence offshoring decisions, e.g. regulations, in particular those regarding the environment. Last but not least, offshoring may also entail gains for developed economies through the improvements in the efficiency of production. In this PhD thesis, several causes and consequences of offshoring are examined empirically for Belgium.<p>The first issue that is investigated is whether offshoring of materials and business services affects industry-level employment. An improved offshoring intensity measure is introduced. It is a volume measure of the share of imported intermediates in output split into materials and business services and according to the country of origin of imports, i.e. high-wage and low-wage countries. Estimations of static and dynamic industry-level labour demand equations augmented by offshoring intensities do not reveal a significant impact of either materials or business services offshoring on total employment for Belgium. This result holds for both the manufacturing sector and the service sector and it proves robust to splitting the manufacturing sector into high-technology and low-technology industries.<p>These results raise the question whether there are actually productivity gains from offshoring. Therefore, estimates of the impact of materials and business services offshoring on industry-level productivity in Belgium are presented. Two features of the analysis are new compared to the existing literature on this subject: the issue is examined separately for manufacturing and market services industries and the possibility of forward and backward spillovers from offshoring, i.e. that productivity gains from offshoring feed through to upstream and downstream industries, is investigated. Results show that materials offshoring has no effect on productivity, while business services offshoring leads to productivity gains in manufacturing. Furthermore, there is no evidence of either forward or backward spillovers from offshoring.<p>Despite the absence of an industry-level total employment effect, offshoring may alter the within-industry composition of employment. In this respect, a major concern is the worsening of the labour market position of low-skilled workers. This issue is addressed by providing evidence on the impact of offshoring on the skill structure of manufacturing employment in Belgium between 1995 and 2007. Offshoring is found to significantly lower the employment share of low-skilled workers. Its contribution to the fall in the employment share of low-skilled workers amounts to 35%. This is mainly driven by offshoring to Central and Eastern European countries. Business services offshoring also contributes significantly to the fall in the low-skilled employment share. As a complement to the existing literature, the widely used current price measure of offshoring is compared with a constant price measure that is based on a deflation with separate price indices for domestic output and imports. This reveals that the former underestimate the extent of offshoring and its impact on low-skilled employment. Finally, further results show that the impact of offshoring on low-skilled employment is significantly smaller in industries with a higher ICT capital intensity.<p>Furthermore, attention is drawn to environmental effects of offshoring by asking whether offshoring contributes to reducing air emissions from manufacturing. Indeed, since the mid-90’s, production-related air emissions in Belgian manufacturing have been reduced substantially. It can be shown that the pace of the reduction has been fastest for domestic intermediates. The issue of whether offshoring has played a role in this reduction by replacing domestic intermediates by imported intermediates is widely debated. Here, a decomposition analysis is developed to measure the contribution of offshoring – the share of imported intermediates in total intermediates – to the fall in air emissions for domestic intermediates. Based on the results from this decomposition analysis, it is possible to calculate that 17% of the fall in greenhouse gas emissions, 6% of the fall in acidifying emissions and 7% of the fall in tropospheric precursor emissions in Belgian manufacturing between 1995 and 2007 can be attributed to offshoring.<p>Finally, emission intensities are also considered as a potential determinant of offshoring. An econometric approach for testing the pollution haven effect for imported intermediate materials is developed. The approach is new with respect to the existing literature on pollution havens through its specific focus on imports of intermediates. The test is embedded in a cost function framework from which a system of cost share equations for variable input factors is derived. The set of potential determinants of the demand for imported intermediate materials includes emission intensities for three types of air pollutants. Their impact constitutes a test of the pollution haven effect. The system of cost share equations is estimated by a within ISUR using data for the Belgian manufacturing sector. Results show some albeit relatively weak evidence of a pollution haven effect for imported intermediate materials.<p> / Doctorat en Sciences économiques et de gestion / info:eu-repo/semantics/nonPublished