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Thesis (MPhil)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: The aim of the study is to investigate the. lifestyles and and romantic relationships of adolescent girls in the Bishop Lavis community. The study also explores the 'taxi-queen' phenomenon as a particular form of relationship. The study employed a qualitative methodology. Data were collected by means of a combination of two methods: firstly, two focus groups each consisting of seven high school learners between the ages of 16 and 18 years and secondly, in-depth interviews conducted with three adolescent girls between the ages of 16 and 20 years who were identified as'taxi-queens'. Regarding lifestyles of the young girls special attention was afforded to leisure activities, the role of the consumer market, domestic circumstances and future expectations. In the case of romantic relationships the study focused on the type of relationship the girls are involved in, reasons for their involvement, the nature and functions of romantic emotions, adolescent dating patterns, sexual behaviour and sexual violence. Regarding lifestyles findings indicate that leisure activities as well as the consumer market playa central role in the lives of these young girls. Leisure activities not only provide pleasure but also function as an escape mechanism from parental supervision, rules and interference. Young girls tend to experience romantic relationships as particularly positive and within these relationships sexuality represents a central component. Sexual activities appear to cornmense during earlier stages of the dating process. Furthermore, such activities are kept secret from parents due to fear of negative reactions and sex-related topics are seldom discussed with parents. Sexual violence often forms a component of romantic relationships between adolescent girls and boys. In conclusion the 'taxi-queen' relationship as a relatively unique form of romantic relationship is demonstrated with reference to the experiences of three young girls involved in such relationships. Recommendations for future research are made on the basis of the findings of this study. / AFRIKAANSE OPSOMMING: Die doel van hierdie studie is om ondersoek in te stel na die lewenstyle en romantiese verhoudings van 'n groep adolessente meisies in die Bishop Lavis gemeenskap. Die studie skenk ook aandag aan die 'taxi-queen' verskynsel as 'n besonderse vorm van romantiese verhouding. 'n Kwalitatiewe metodologiese benadering is gevolg. Data insameling het 'n kombinasie van twee metodes behels: eerstens, twee fokusgroepe bestaande uit sewe hoerskoolmeisies elk tussen die ouderdomme van 16 en 18 jaar en tweedens, in-diepte onderhoude met drie adolessente meisies tussen die ouderdom van 16 en 20 jaar wat as 'taxi queens' geidentifiseer is. Wat lewenstyle vanjong meisies betrefis daar veral gefokus op vryetydsbesteding, die rol van die verbruikersmark, huishoudelike omstandighede en toekomsverwagtinge van die groep meisies. Met betrekking tot romantiese verhoudings is daar hoofsaaklik op die volgende aspekte gefokus: die tipe verboudings waarin die meisies betrokke is, die redes vir hul betrokkenheid, die aard en funksies van romantiese emosies; adolessente hofmakery, die voorkoms van seksuele gedrag, seksuele geweld en dwang. Die studie bevind dat vryetydbesteding en die verbruikermark 'n sentrale rol in die lewe van hierdie meisies speeL Benewens die plesier wat daaruit geput word, funksioneer vryetydbesteding as 'n ontsnappingsmeganisme van ouerlike toesig, reels en inmenging van die kant van ouers. Die studie bevind verder dat jong meisies romantiese verhoudings as besonder positief beleef. Binne sodanige verhoudings verteenwoordig seksualiteit 'n sentrale komponent en seksuele aktiwiteite neem in aanvang tydens 'n vroee stadium in die proses van hofinakery. Betrokkenheid by seksuele aktiwiteite word vir ouers geheim gehou uit vrees vir negatiewe evaluering en jong meisies kommunikeer selde met hul ouers oor sekverwante onderwerpe. Verder is bevind dat seksuele geweld dikwels 'n komponent vorm van romantiese verhoudings tussen adolessente meisies en seuns. Ten slotte word die besonderse aard van die sogenaamde 'taxi-queen' verhouding beklemtoon aan die hand van die ervaringe van drie jong meisies betrokke by sodanige verhoudings. Op grond van die studie word daar aanbevelings vir verdere navorsing gemaak.

Taxis équipés de capteurs GPS sont un dispositif sensoriel important pour examiner les mouvements et les activités des gens. Dans cette thèse, nous cherchons à découvrir les facettes cachées en ce qui concerne les dynamiques sociales et communautaires codés dans les données de taxi GPS pour mieux comprendre comment se comporte la population urbaine et la dynamique résultant de la ville. Comme certains « aspects cachés» sont en ce qui concerne l'aspect similaire de la dynamique sociale et de la communauté, nous avons encore définissons formellement trois catégories pour l'étude, et les explorer à combler les écarts importants entre la première circuler des données GPS et des applications innovantes et des services urbains intelligents. Plus précisément, 1. Pour permettre aux applications d'alertes de fraude de taxi en temps réel, nous vous proposons algorithme iBoat qui est capable de détecter des trajectoires anormales "à la volée " et déterminer quelles parties de la trajectoire sont responsables de sa "anomalousness", en les comparant historiquement trajectoires ayant la même origine et de destination. 2. Pour introduire des services de transport respectueux de l'environnement aux citoyens rentable et, nous vous proposons B -Planner qui est une approche en deux phases, à planifier des itinéraires de bus de nuit bi- directionnelles de levier grands taxis données GPS. 3. Afin d'offrir un système de planification voyage d'itinéraire personnalisé, interactif, et le trafic-courant pour les utilisateurs, nous proposons système Tripplanner qui contient à la fois hors ligne et des procédures en ligne, en s'appuyant sur une combinaison de géolocalisation réseau social et des ensembles de données de taxi GPS. Enfin, certaines directions de recherche prometteuses pour les travaux futurs sont signalées, qui tentent essentiellement de fusionner les données de taxi GPS avec d'autres ensembles de données pour fournir des services urbains plus intelligents et personnalisés / Taxis equipped with GPS sensors are an important sensory device for examining people’s movements and activities. They are not constrained to a pre-defined schedule/route. Big taxi GPS data recording the spatio-temporal traces left by taxis provides rich and detailed glimpse into the motivations, behaviours, and resulting dynamics of a city’s mobile population through the road network. In this dissertation, we aim to uncover the “hidden facets” regarding social and community dynamics encoded in the taxi GPS data to better understand how urban population behaves and the resulting dynamics in the city. As some “hidden facets” are with regard to similar aspect of social and community dynamics, we further formally define three categories for study (i.e. social dynamics, traffic dynamics, and operational dynamics), and explore them to fill the wide gaps between the raw taxi GPS data and innovative applications and smart urban services. Specifically, 1. To enable applications of real-time taxi fraud alerts, we propose iBOAT algorithm which is capable of detecting anomalous trajectories “on-the-fly” and identifying which parts of the trajectory are responsible for its anomalousness, by comparing them against historically trajectories having the same origin and destination. 2. To introduce cost-effective and environment-friendly transport services to citizens, we propose B-Planner which is a two-phase approach, to plan bi-directional night bus routes leveraging big taxi GPS data. 3. To offer a personalized, interactive, and traffic-aware trip route planning system to users, we propose TripPlanner system which contains both offline and online procedures, leveraging a combination of Location-based Social Network (i.e. LBSN) and taxi GPS data sets. Finally, some promising research directions for future work are pointed out, which mainly attempt to fuse taxi GPS data with other data sets to provide smarter and personalized urban services for citizens

M. Tech. (Department of Accountancy, Faculty of Management Sciences), Vaal University of Technology. / The minibus taxi industry in South Africa is one of the biggest, fastest growing, and riskiest industries in the world. The minibus taxi industry contributes to the economy by creating over 600,000 jobs, providing fast and cheap transport and fighting poverty and unemployment. However, the recent COVID 19 pandemia restrictions has caused a sudden and movement of economic growth and competition has forced the minibus taxi industry to be competitive in all aspects. This has resulted in intense competition for minibus taxi owners. Minibus taxi owners are constantly in rivalry amongst themselves and with other public road transport providers. In early 1988, the minibus taxi industry started seeing an influx in the number of new minibus taxis and minibus owners. This influx created problems of competition within the industry and among minibus taxi owners. Due to the importance of this industry, this research study investigated whether minibus taxi owners in the Emfuleni Local Municipality apply selected management accounting principles in the management of their minibus taxi businesses. Selected management accounting principles in this study refers to cost volume profit analysis, cost structure, and budgeting. This research study followed a quantitative research design and a questionnaire was used to collect primary data from a census of 500 minibus taxi owners from the following five associations: Get Ahead Taxi Association (GATA), Vaal National Taxi Association (VNTA), Vanderbijlpark Taxi Association (VTA), Sharpeville to Vereeniging and Vanderbijlpark Taxi Association (SVVTA) and Civic Centre Taxi Association (CCTA) operating in the Emfuleni Local Municipality. Using descriptive statistical analysis to present the findings, the study used Statistical Package for Social Sciences Version 27. Findings obtained using an online questionnaire and printed questionnaire distributed revealed a lack of management accounting principles application among these minibus taxi owners. Furthermore, the minibus taxi owners do not apply cost volume profit analysis and most do not use budgets. However, it was found that some minibus taxi owners apply very basic cash budgeting through a pen-on-paper approach. It was also found that minibus taxi owners understand the application of cost structures. This research study recommends that minibus taxi owners should be offered training by skills sectors to apply the selected management accounting principles. The limitations of this research study included that the census was geogracial restrictions, level of education, and corona virus restrictions. Despite these limitations, the research study was able to fulfil its main objective by determining that majority of minibus taxi owners do not apply the selected management accounting principles.

[pt] A dissertação em tela foi desenvolvida com o intuito de proporcionar ao professor de matemática uma introdução ao estudo das Geometrias Não Euclidianas, um assunto carente em nossas salas de aulas tanto do Ensino Básico como das Licenciaturas em Matemática. Em consonância com os Parâmetros Curriculares Nacionais, são historicamente construídos os conhecimentos matemáticos apresentados para discutir o Quinto Postulado dos Elementos de Euclides e para apresentar a descoberta de novas geometrias. Para ser apresentada de forma mais detalhada, foi escolhida uma Geometria Não Euclidiana que pode ser facilmente entendida e contextualizada por alunos do Ensino Médio: a Geometria do Táxi. Tal geometria, além de possibilitar ligações com outros conteúdos do Ensino Básico também é um modelo para a geografia urbana, oferecendo ao alunado a possibilidade de interação com questões motivadoras, interdisciplinares e próximas do seu cotidiano. É apresentada uma sugestão de dinâmica que compara os conceitos das distâncias euclidiana e do táxi além de discutir a definição de circunferência e sua representação tanto na Geometria Euclidiana como na Geometria do Táxi. Além disso, alguns resultados da aplicação da referida dinâmica em turmas do 3o. ano do Ensino Médio do C.E. Professor Ney Cidade Palmeiro, localizado na cidade de Itaguaí no Rio de Janeiro, também são relatados. Pretende-se que este trabalho seja mais uma contribuição para o aprimoramento da formação continuada dos professores das escolas de ensino básico no país. / [en] The present dissertation was developed with the intention of providing the mathematics teacher an introduction to the study of Non Euclidean Geometry, one lacking subject in our classrooms as much as the basic education and undergraduate mathematics. In line with the National Curriculum Parameters, mathematical knowledge presented to discuss the Fifth Postulate of Euclid s Elements, and to present the discovery of new geometries are historically constructed. To be presented in more details, we choose a non Euclidean Geometry that can be easily understood and contextualized by high school students: the Taxicab Geometry. This geometry, in addition to allowing connections with other content of basic education, such geometry is a model for urban geography, offering the pupils the opportunity to their everyday issues. A suggested activity to be developed in the classroom by students who compares the concepts of taxi distance and euclidean distance and besides discussing the definition of a circle and its representation in both Euclidean Geometry as in the Taxi appears. Futhermore, some results of implementing this activity in class 3rd. year of high school the Colégio Estadual Professor Ney Cidade Palmeiro, located in Itaguaí in Rio de Janeiro, are also reported. It is intended that this work is a futher contribuition to the improvement of continuing education of teachers of primary schools in the country.

Background: In recent years, the Swedish taxi industry has undergone a number of changes as a result of increased digitalisation in a deregulated market. Most market players have emerged as a result of the freedom of establishment, which in turn has led to higher competition. Among these new entrants, the ride-hailing business model has had an impact by taking a traditional service and performing it differently. This thesis will thus examine how this approach has affected the Swedish taxi industry in more detail. Purpose: The thesis aims to increase understanding of the aspects of the ride-hailing business model that are specifically distinguished by the company Uber. The following secondary purpose is to identify the impact this specific business model has on the Swedish taxi industry as a result of Uber's establishment on the Swedish market. Method: The thesis is an abductive case study of qualitative character. The empirical data has been collected through three distinct approaches, which are the collection of scientific material, semi-structured interviews with three respondents and a Social Media Analysis consisting of data from approximately 100 independent articles and media publications. Furthermore, these three types of empirical data have been selected via a strategic selection. Conclusion: The result of this thesis shows that the specific aspects that stand out in Uber Sweden's use of the ride-hailing business model are value creation, differentiation, innovation and social acceptance. The results also show that the ride-hailing business model has influenced the Swedish taxi industry in terms of the specific aspects' influence on the development of the taxi market and on government regulations. / Bakgrund: Under de senaste åren har den svenska taximarknaden genomgått en rad förändringar till följd av en ökad digitalisering på en avreglerad marknad. Det har uppkommit flertalet aktörer på marknaden till följd av den fria etableringsrätten, som i sin tur lett till en högre konkurrens. Bland dessa nya aktörer har affärsmodellen ride-hailing fått ett genomslag genom att ta en traditionell tjänst och utföra den annorlunda. Uppsatsen kommer därmed att närmare undersöka hur detta tillvägagångssätt har påverkat den svenska taximarknaden. Syfte: Uppsatsen syftar till att öka förståelsen för de aspekter av ride-hailing-affärsmodellen som specifikt utmärker sig hos företaget Uber. Det följande sekundära syftet avser att identifiera den påverkan som denna specifika affärsmodell haft på den svenska taxibranschen till följd av Ubers etablering på den svenska marknaden. Metod: Uppsatsen är en abduktiv fallstudie av kvalitativ karaktär. Empiri har insamlats via tre distinkta tillvägagångssätt, vilka är insamlande av vetenskapligt material, semistrukturerade intervjuer med tre respondenter samt en Social Media Analys bestående av data från cirka 100 fristående artiklar samt mediala publikationer. Vidare har dessa tre typer av empiriska data valts ut via ett strategiskt urval. Slutsats: Resultatet från denna uppsats visar att de specifika aspekterna som utmärker sig inom Uber Sveriges användning av ride-hailing-affärsmodellen är värdeskapande, differentiering, innovation och social acceptans. Vidare visar resultatet på att ride-hailing-affärsmodellen har påverkat den svenska taximarknaden i avseende på de specifika aspekternas inflytande på utvecklingen av taxibranschen samt kring statliga regleringar.

Student Number : 0312394F - MPH research report - School of Public Health - Faculty of Health Sciences / Introduction: Human Immunodeficiency Virus (HIV) was first isolated from human blood in 1983 at the Pasteur Institute, Paris. Currently there is no cure for HIV and control efforts emphasize prevention. One of the components of the Global Strategy put forward to preventing HIV transmission is HIV Voluntary Counselling and Testing (VCT) (Ginwalla, Grant & Day:2002). Taxi drivers are part of the Ugandan population at special risk of acquiring this virus. It was therefore necessary to carry out a study in this group of people to assess how much they knew about HIV/VCT services. Study Objectives To establish the level of knowledge amongst the taxi drivers about the availability and accessibility of HIV VCT services in Kampala. To identify factors that influence the taxi drivers in Kampala, Uganda to access the VCT services. Methods and materials A cross-sectional descriptive study design was used to carry out the study amongst 400 taxi drivers who consented to participate and operated within and around the city of Kampala during 2004. A structured questionnaire to record variables that included, age, sex, marital status, level of education, level of knowledge of VCT, factors that enhance VCT uptake, factors that inhibit VCT uptake, history of having ever had VCT, and knowledge of spouse or sexual partner’s HIV serostatus, was used. Data was entered into EPI-INFO 6 computer program and descriptive and analytic investigation using proportion or percentages to compare the level of knowledge generated was used. Findings/Results A total of 399 taxi drivers with 52.8% of them aged between 26 – 35 years participated in the study. 68.8% lived within 6 km of the city centre. All were married and 78.8% had one spouse. 0.75% were lady drivers. 55% of the participants had attained secondary school level of education. 69% of the taxi drivers knew that HIV/AIDS was the commonest health problem in the country and 57.4% of the participants mentioned HIV testing as the only way one would ascertain their serostatus. 94.2% had heard about HIV/VCT mainly from the media and as much as 98.7% of the taxi drivers knew a place where such services could be got. 82.2% confirmed that these places were accessible and 85.9% said that the services were not expensive. However, 57.3% of the participants preferred getting these services where they were known in order to get genuine results and subsequent support. The 26% who opposed this idea sighted confidentiality as the main obstacle. Despite the knowledge level about HIV/VCT amongst the participants, 68.3% of the communal taxi drivers were willing to go for the service and only 16.1% had actually taken the test. Out of the 399 participants 59.6% felt that they could share their serostatus with their spouses. Conclusion The taxi drivers are knowledgeable about HIV/VCT services and these findings lie within the overall range of knowledge of the population in urban Uganda. The HIV/VCT services are accessible and affordable to the taxi drivers but the fear to receive the unexpected results and the consequences of having positive results hinder the taxi drivers from seeking the VCT services. The majority of taxi drivers preferred to go to HIV/VCT service points where they were known. This factor could have contributed to the small number of taxi drivers that had taken the test. Probably few suitable service points to go to had been identified by these taxi drivers. Recommendations The government and other organizations that provide care in the field of HIV should organize sensitization seminars for taxi drivers to address issues aimed at allaying their anxiety or fear to receive positive results. Also, there is a need to intensify counselling services for the taxi drivers by establishing counselling centres close to the two taxi parks in the City. HIV/VCT service centres should be integrated with other health services so that people who seek either of the services can gain from both. This will encourage more taxi drivers to come to these centres.

Kisoro, a rural district in Uganda, is undergoing various transformations which could be summarized under the term neoliberal development. This qualitative study, which is based on six weeks of anthropological fieldwork, is focused on how a few individuals working as motorcycle-taxi drivers in the area experience these transformations, and how they deal with them. The results indicate that while they tend to describe them as “development”, they see them as constituting an uneven form of development - not beneficial to all, something which, in their view, makes this development less genuine. It is commonly associated with various “others”; carried out by and for others, while the informants have to live off the leftovers from it, were the motorcycle-taxi job is seen as such a leftover; neither enabling much upward - nor geographical - mobility. In some cases, they feel included in transformations which makes things worse, so it all constitutes not only a limited, but a somehow distorted development, and there is nostalgia around better pasts. But simultaneously, many also feel free, and as their hopes for inclusion in a genuine development erodes while they wait for it, inspiration from an external world makes them strive for a more individualized prosperity.

Made available in DSpace on 2016-08-10T10:54:52Z (GMT). No. of bitstreams: 1 LUCIANO FERREIRA FREITAS.pdf: 1085209 bytes, checksum: 8cb6cea15bb3c1928d3054d4967c8bf7 (MD5) Previous issue date: 2015-10-02 / This study aims to evaluate the quality of life as well as the relationship of this with the socioeconomic and demographic profile and the length of service of workers motorcycle taxi drivers in the city of Aparecida de Goiânia-GO. For this, we carried out an analytical study of the quantitative cross-sectional with a sample of 133 male motorcycle taxi drivers. To check the profile of these workers, a sociodemographic questionnaire and the socioeconomic questionnaire was applied, Criteria of Economic Classification Brazil (CCEB). To assess quality of life, the WHO Quality of Life (WHOQOL-BREF) questionnaire and the Short Form Health Survey (SF-36) were used. Regarding sociodemographic profiles, there was a predominance of workers, married (53.4%), with up to two children (78.9%), aged 18-40 years old (56.4%), primary school education(64 7%), between one and five years of professional practice (57.9%), and belonging to the C economic class (66.2%). Concerning quality of life, WHOQOL-Bref, it was found that the domain "environment" (52.09) and the domain "social relations" (68.23) were the ones with lowest score and the best scores obtained were in "physical" domain (74.89) and "psychological" (70.52). In the SF-36, the domain "pain" (49.59) is the most negative impact on the quality of life of these professionals and the domain "functional capacity" (81.17) was the one who got the best score. Comparing the demographic data and the length of service with the quality of life WHOQOL-Bref, significant differences in the field "environment" (p = 0.029), indicating that the group with the lowest function of time had worse quality of life that the group with greater seniority. In the SF-36, there was a significant difference in the fields "vitality" (p = 0.025) and "mental health" (p = 0.005) relative to the variable "marital status" in which the married participants had better quality of life in these areas. There was also a significant difference on "vitality" (p = 0.029) relative to the variable "age in years", indicating that the age group up to 40 years had worse quality of life compared to the older group. Compared to the variable "schooling" there was significant difference in the field "general health" (p = 0.047) in those with primary education had a poorer quality of life to those with high school. There was a significant difference in the field "vitality" (p = 0.020) compared to the variable "function of time" in which the group with the shortest time had worse quality of life compared to the older group. When comparing the WHOQOL-Bref with socioeconomic data for all economic classes, the highest score was the "physical" domain and the lowest was in the field "environment." In the analysis of the areas of the SF-36 compared to the socioeconomic data, significant differences were found in the domain "pain" (p = 0.005), indicating the participants in classes D and E with worse quality of life compared to the B and C classes. This study has highlighted the need to implement strategies for improving the quality of life of this class of workers. / Este trabalho tem por objetivo avaliar a qualidade de vida, bem como as relações dessa com o perfil socioeconômico e sociodemográfico e o tempo de serviço dos trabalhadores mototaxistas da cidade de Aparecida de Goiânia-GO. Para isso, foi realizado um estudo analítico do tipo transversal quantitativo com uma amostra de 133 mototaxistas do sexo masculino. Para verificar o perfil desses trabalhadores, foi aplicado um questionário sociodemográfico e o questionário socioeconômico, Critério de Classificação Econômica do Brasil (CCEB). Para avaliar a qualidade de vida desses mototaxistas, utilizaram-se dois instrumentos, o Whoqol-Bref e o SF-36. Quanto ao perfil sociodemográfico, verificou-se a predominância de trabalhadores, casados (53,4%), com até dois filhos (78,9%), faixa etária de 18 a 40 anos (56,4%), ensino fundamental (64,7%), entre um a cinco anos de exercício da profissão (57,9%), e pertencentes à classe econômica C (66,2%). Em relação à qualidade de vida, no Whoqol-Bref, o domínio meio ambiente (52,09) e relações sociais (68,23) foram os de menor escore e os melhores foram no domínio físico (74,89) e no psicológico (70,52). No SF-36, o domínio dor (49,59) é o que mais interfere negativamente na qualidade de vida desses profissionais e o domínio capacidade funcional (81,17) foi o que obteve o melhor escore. Na comparação entre os dados sociodemográficos e o tempo de serviço com a qualidade de vida do Whoqol-Bref, houve diferença significativa no domínio meio ambiente (p=0,029), indicando que o grupo com menor tempo de função teve pior qualidade de vida em relação ao grupo com maior tempo de serviço. No SF-36, houve uma diferença significativa nos domínios vitalidade (p=0,025) e saúde mental (p=0,005) em relação à variável estado civil , em que os participantes casados apresentaram melhor qualidade de vida nestes domínios. Houve uma diferença significativa também no domínio vitalidade (p=0,029) em relação à variável idade em anos , indicando que o grupo com idade até 40 anos teve pior qualidade de vida em relação ao grupo mais velho. Na comparação com a variável escolaridade , houve diferença significativa no domínio estado geral de saúde (p=0,047), em que aqueles com ensino fundamental apresentaram pior qualidade de vida aos que possuem ensino médio. Houve diferença significativa no domínio vitalidade (p=0,020) na comparação com a variável tempo de função , em que o grupo com menor tempo teve pior qualidade de vida em relação ao grupo mais antigo. Ao comparar o Whoqol-Bref com os dados socioeconômicos, para todas as classes econômicas, a maior pontuação foi no domínio físico e a menor foi no domínio meio ambiente . Na análise dos domínios do SF-36 em comparação com os dados socioeconômicos, houve diferença significativa no domínio dor (p=0,005) indicando os participantes das classes D e E com pior qualidade de vida em relação aos das classes B e C. Este estudo permitiu evidenciar a necessidade de implantar estratégias em prol da melhoria da qualidade de vida dessa classe de trabalhadores.

La thèse porte sur l'effet de politiques publiques visant à agir sur le fonctionnement concurrentiel des marchés, en traitant une question de politique de la concurrence et une question de régulation sectorielle. La première partie de la thèse porte sur le contrôle des concentrations : elle examine tout d'abord les effets des concentrations sur les prix des biens produits, avant de rendre endogène la décision de l'autorité de concurrence. Un premier article examine si l'un des objectifs justifiant l'existence d'un contrôle de la concurrence - l'amélioration du surplus des consommateurs - est bien atteint en pratique dans le cas du contrôle des concentrations, par l'estimation empirique de l'effet des concentrations sur les prix des biens et services vendus dans les secteurs concernés, à partir de données françaises multisectorielles. Dans un deuxième article, la prise de décision d'une autorité de concurrence est examinée, par une analyse empirique des déterminants des avis du Conseil de la concurrence en matière de concentration. La seconde partie de la thèse porte sur un problème de régulation : comment les restrictions à la libre entrée sont valorisées par les acteurs présents sur le marché, du fait des profits anticipés, et quels sont les déterminants de cette valeur. Cette question est examinée dans deux situations : tout d'abord, la valorisation des fréquences du " dividende numérique ", qui sont libérées par l'extinction de la diffusion analogique de la télévision ; ensuite, la valeur d'une licence de taxi, dont l'élasticité au nombre de licences attribuées est estimée.