This dissertation consists of three chapters that aim to build a framework which can be used to study interactions between the labour market and macroeconomic dynamics. To achieve this, we reformulate a standard New Keynesian dynamic stochastic general equilibrium (DSGE) model to include search and matching frictions in the labour market and heterogeneity in price and wage stickiness. The first chapter, coauthored with Professor Engin Kara, builds a real business cycle model with labour search frictions and heterogeneity in wage stickiness. Shimer’s (2005) critique on labour search models, that it cannot explain observed unemployment movements, reignited a long-standing debate on unemployment fluctuations and wage determination. Gertler and Trigari (2009) introduce wage stickiness to the model to match unemployment volatility, while Pissarides (2009) finds this modification not satisfactory, citing evidence on high wage cyclicality. We find heterogeneity in wage stickiness in microdata on wages. Our model, which reflects this heterogeneity, matches the data better than its one sector alternatives. The second chapter, coauthored with Professor Engin Kara, studies output dynamics in New Keynesian models with the standard labour market and heterogeneity in price stickiness. We analytically and numerically show that these models can reproduce a hump-shaped output response to persistent monetary shocks, which is a key feature of monetary transmission mechanism. The version of models without heterogeneity cannot generate a hump. Flexible prices in models with heterogeneity play a crucial role, by generating inertia to price-setting and output. The third chapter studies how the labour search frictions affect output dynamics in New Keynesian models, when combined with heterogeneity in nominal rigidities. Long-term employment relationship, that arises under search and matching framework, makes marginal costs history dependent. We show that this history dependence generates inertia in the model. Heterogeneity in nominal rigidities significantly reinforces this inertia, resulting in a hump-shaped output response to persistent monetary shocks. The model without the search frictions cannot replicate a hump even when monetary shocks are persistent, when wages are sticky.

This dissertation presents three essays that focus on various aspects pertaining to the management of online platforms, defined as "digital services that facilitate interactions between two or more distinct, but interdependent sets of users (whether firms or individuals) who interact through the service via the Internet" (OECD, 2019). The interactions benefit both the users and the platform. Managing online platforms involves developing strategies for one or more of three value adding functions: (a) lowering search costs for the parties connecting through the platform, (b) providing a technology infrastructure that facilitates transactions at scale by sharing both demand and supply side costs; and (c) locating other audiences or consumers for the output that results from the transaction. The platform manager must manage these value adding functions. Thus, one important management task is to recognize potential asymmetries in the economic and/or psychological motivations of the transacting parties connected through the platform. In this dissertation, I empirically examine these issues in greater detail. The first essay, "Incentivizing User-Generated Content—A Double-Edged Sword: Evidence from Field Data and a Controlled Experiment," addresses the conundrum faced by online platform managers interested in crowdsourcing user-generated content (UGC) in prosocial contexts. The dilemma stems from the fact that offering monetary incentives to stimulate UGC contributions also has a damping effect on peer approval, which is an important source of non-monetary recognition valued by UGC contributors in prosocial contexts. The second essay, "Matching and Making in Matchmaking Platforms: A Structural Analysis," examines matchmaking platforms, focusing specifically on the problem of misaligned incentives between the platform and the agents. Based on data from the Ultimate Fighting Championship (UFC) on fighter characteristics, and pay-per-view revenues associated with specific bouts, we identify the potential for conflicts of interest and examine strategies that may be used to mitigate such problems. The third essay, "Matching and Making in Matching Markets: A Managerial Decision Calculus," extends the empirical model and analytical work to a class of commonly encountered one-sided matching market problems. It provides the conceptual outline of a decision calculus that allows managers to explore the revenue and profitability implications of adaptive changes to the tier structures and matching algorithms. / Doctor of Philosophy / The 21st century has witnessed the rise of the platform economy. Consumers routinely interact with online platforms ways in their day to day activities. For instance, they interact with platforms such as Quora, StackOverflow, Uber, and Airbnb to name only a few. Such platforms address a variety of needs starting from providing users with answers to a variety of questions to matching them with a range of service providers (e.g., for travel and dining needs). However, the rapid growth of the platform economy has created a knowledge gap for both consumers and platforms. The three essays in this dissertation attempt to contribute to the literature in this area. The first essay, "Incentivizing User-Generated Content—A Double-Edged Sword: Evidence from Field Data and a Controlled Experiment," examines how crowdsourcing contests influence the quantity and quality of user-generated content (UGC). Analyzing data from the popular question and answer website Quora, we find that offering monetary incentives to stimulate UGC contributions increases contributions but also has a simultaneous damping effect on peer endorsement, which is an important source of non-monetary recognition for UGC contributors in prosocial contexts. The second essay, "Matching and Making in Matchmaking Platforms: A Structural Analysis," examines matchmaking platforms, focusing on the problem of misaligned incentives between the platform and the agents. Based on data from the Ultimate Fighting Championship (UFC) on fighter characteristics, and pay-per-view revenues associated with specific bouts, we identify the potential for conflicts of interest and examine strategies that may be used to mitigate such problems. The third essay, "Matching and Making in Matching Markets: A Managerial Decision Calculus," extends the empirical model and analytical work to a class of commonly encountered one-sided matching market problems. It provides the conceptual outline of a decision calculus that allows managers to explore the revenue and profitability implications of adaptive changes to the tier structures and matching algorithms.

La thèse étudie les liens qui existent entre les recommandations issues de la littérature sur l'assurance chômage optimale et la qualité des emplois repris par les chômeurs. Nous nous intéressons en particulier à une dimension de la qualité de l'emploi qu'est la stabilité des emplois dans un contexte où les contrats de courte voire de très courte durée sont en pleine expansion en France. En utilisant les modèles théoriques de recherche d'emploi et d'appariement, nous analysons la manière dont les caractéristiques de l'assurance chômage affectent la stabilité des emplois repris. La particularité de notre analyse consiste à intégrer la manière dont les employés sont influencés par les paramètres de l'assurance chômage. En effet, si l'on souhaite analyser de manière globale l'impact des paramètres du système d'indemnisation sur l'évolution du taux de chômage, il convient de déterminer comment ces derniers influencent le taux de sortie du chômage (analyse du comportement des demandeurs d'emploi) mais aussi comment ils affectent le taux d'entrée au chômage (analyse du comportement des employés). Pour étudier le comportement des employés nous considérons que ces derniers influencent leur probabilité de conserver leur emploi en fournissant des efforts de rétention d'emploi. Nous montrons notamment que les chômeurs qui quittent rapidement le chômage retrouvent fréquemment des emplois peu stables. Une fois en emploi, ils exercent relativement peu d'efforts pour conserver leur emploi augmentant par là même leur probabilité de retourner rapidement au chômage. L'impact final d'une réduction du montant de l'indemnisation sur l'évolution du chômage est donc indéterminé dès lors que l'on intègre les employés dans l'analyse. / The thesis studies the relationships between the Optimal Unemployment Insurance (UI) literature recommendations and post unemployment job stability. We focus on one particular job quality dimension that is job stability within a context of a huge increase of very short duration job contracts in France since the 2000’s. Using job search and matching frameworks, we analyse how the features of the UI system affect job stability. The particularity of our approach is that we account for employees’ behaviors while the majority of the literature on optimal UI focuses only on jobless workers behaviors. We show notably that job-seekers who leave quickly unemployment tend to find unstable jobs. Once employed they have a greater probability to return to unemployment because the job-retention efforts they exert are not sufficient.

Dans le cadre du projet GUIMUTEIC, qui vise à équiper les visiteurs de musées d'un outils d'aide à la visite équipé d'une caméra, cette thèse adresse le problème d'accès à l'information en mobilité.On s'intéresse à comment rendre l'information à propos des œuvres accessible et automatique aux visiteurs de lieux touristiques.Elle s'inscrit dans le cadre du projet GUIMUTEIC, qui vise à équiper les visiteurs de musées d'un outil d'aide à l'accès à l'information en mobilité.Être capable de déterminer si le visiteur désire avoir accès à l'information signifie identifier le contexte autour de lui, afin de fournir une réponse adaptée, et réagir à ses actions.Ceci soulève les problématiques d'identification de points d'intérêts, pour déterminer le contexte, et d'identification de gestes de utilisateurs, pour répondre à ses demandes.Dans le cadre du notre projet, le visiteur est donc équipé d'une caméra embarquée.L'objectif est de fournir un solution à l'aide à la visite, en developpant des méthodes de vision pour l'identification d'objet, et de detection de gestes dans les vidéos à la première personne.Nous proposons dans cette thèse une étude de la faisabilité et de l'intérêt de l'aide à la visite, ainsi que de la pertinence des gestes dans le cadre de l'interaction avec un système embarqué.Nous proposons une nouvelle approche pour l'identification d'objets grâce à des réseaux de neurones profonds siamois pour l'apprentissage de similarité entre les images, avec apprentissage des régions d'intérêt dans l'image.Nous explorons également l'utilisation de réseaux à taille réduite pour le détection de gestes en mobilité.Nous présentons pour cela une architecture utilisant un nouveau type de bloc de convolutions, pour réduire le nombre de paramètres du réseau et permettre son utilisation sur processeur mobile.Pour évaluer nos propositions, nous nous appuyons sur plusieurs corpus de recherche d'image et de gestes, crée spécialement pour correspondre aux contraintes du projet. / This thesis is part of the GUIMUTEIC project, which aim is to equip museum tourist with an audio-guide enhanced by a camera.This thesis adress the problem of information access in mobile environment, by automaticaly providing information about museum artefacts.To be able to give this information, we need to know when the visitor desire guidance, and what he is looking at, to give the correct response.This raises issues of identification of points of interest, to determine the context, and identification of user gestures, to meet his demands.As part of our project, the visitor is equipped with an embedded camera.The goal is to provide a solution to help with the visit, developing vision methods for object identification, and gesture detection in first-person videos.We propose in this thesis a study of the feasibility and the interest of the assistance to the visit, as well as the relevance of the gestures in the context of the interaction with an embedded system.We propose a new approach for objects identification thanks to siamese neural networks to learn images similarity and define regions of interest.We are also exploring the use of small networks for gesture recognition in mobility.We present for this an architecture using new types of convolution blocks, to reduce the number of parameters of the network and allow its use on mobile processor.To evaluate our proposals, we rely on several corpus of image search and gestures, specificaly designed to match the constraints of the project.

“History matching” (model calibration, parameter identification) is an established method for determination of representative reservoir properties such as permeability, porosity, relative permeability and fault transmissibility from a measured production history; however the uniqueness of selected model is always a challenge in a successful history matching. Up to now, the uniqueness of history matching results in practice can be assessed only after individual and technical experience and/or by repeating history matching with different reservoir models (different sets of parameters as the starting guess). The present study has been used the stochastical theory of Kullback & Leibler (K-L) and its further development by Akaike (AIC) for the first time to solve the uniqueness problem in reservoir engineering. In addition - based on the AIC principle and the principle of parsimony - a penalty term for OF has been empirically formulated regarding geoscientific and technical considerations. Finally a new formulation (Penalized Objective Function, POF) has been developed for model selection in reservoir history matching and has been tested successfully in a North German gas field. / „History Matching“ (Modell-Kalibrierung, Parameter Identifikation) ist eine bewährte Methode zur Bestimmung repräsentativer Reservoireigenschaften, wie Permeabilität, Porosität, relative Permeabilitätsfunktionen und Störungs-Transmissibilitäten aus einer gemessenen Produktionsgeschichte (history). Bis heute kann die Eindeutigkeit der identifizierten Parameter in der Praxis nicht konstruktiv nachgewiesen werden. Die Resultate eines History-Match können nur nach individueller Erfahrung und/oder durch vielmalige History-Match-Versuche mit verschiedenen Reservoirmodellen (verschiedenen Parametersätzen als Startposition) auf ihre Eindeutigkeit bewertet werden. Die vorliegende Studie hat die im Reservoir Engineering erstmals eingesetzte stochastische Theorie von Kullback & Leibler (K-L) und ihre Weiterentwicklung nach Akaike (AIC) als Basis für die Bewertung des Eindeutigkeitsproblems genutzt. Schließlich wurde das AIC-Prinzip als empirischer Strafterm aus geowissenschaftlichen und technischen Überlegungen formuliert. Der neu formulierte Strafterm (Penalized Objective Function, POF) wurde für das History Matching eines norddeutschen Erdgasfeldes erfolgreich getestet.

Invasive exotic species threaten the biodiversity and function of native ecosystems. Existing models, attempting to predict and control successful invaders, often emphasize isolated stages of in their life history and fail to formalize interactions between exotic species and recipient environments. In order to elucidate key mechanisms in the success of select invaders, I investigated the role of dispersal, establishment, proliferation, and persistence in their threat to natural areas. Focusing on Riding Mountain National Park, Manitoba, Canada, I integrated the native climatic range and biological traits of 251 exotic vascular plants reported inside and outside the park. Based on their climatic range in Europe, 155 among 174 exotic plant species absent from the Park were predicted to establish within its boundaries; among these, 40 clonal perennials were considered the highest threat to the Park’s biodiversity. Focusing on smooth brome (Bromus inermis Leyss.), a Eurasian perennial, threatening the structure and function of native prairies throughout the Great Plains, I extended my research to investigate the role of dispersal, establishment, proliferation, and persistence in characterizing its threat to the endemic diversity of northern fescue prairies, protected within Riding Mountain National Park. Patterns of smooth brome invasions were contingent on the type of propagules dispersed. The shallow dispersal gradient of individual florets combined with the steeper gradient of panicles and spikelets suggested that smooth brome is capable of simultaneously invading along dense fronts as well as by establishing isolated foci. While low correlations between the number of dispersed seeds and their recruitment suggested post-dispersal transport, seedling establishment remained contingent on prairie diversity. Seedling biomass increased with declining plant diversity, however, its impact depended on the availability of soil nitrogen. As a result, disturbed areas, preserving the root function of native plants, resisted smooth brome establishment. Even though low nitrogen contributed to a decline in seedling biomass, physiological integration between ramets facilitated their vegetative proliferation in low resource environments. Despite its rapid establishment and proliferation, smooth brome productivity declined at the center of invading clones. Although field and greenhouse observations failed to implicate soilborne pathogens, reasons for the observed decline remain unresolved. My research demonstrates that while Riding Mountain National Park and other natural areas in western Canada will continue to be impacted by exotic plants, integrating key stages in their life history provides an important conceptual framework in predicting their threat to natural areas and prioritizing management. / October 2008

Invasive exotic species threaten the biodiversity and function of native ecosystems. Existing models, attempting to predict and control successful invaders, often emphasize isolated stages of in their life history and fail to formalize interactions between exotic species and recipient environments. In order to elucidate key mechanisms in the success of select invaders, I investigated the role of dispersal, establishment, proliferation, and persistence in their threat to natural areas. Focusing on Riding Mountain National Park, Manitoba, Canada, I integrated the native climatic range and biological traits of 251 exotic vascular plants reported inside and outside the park. Based on their climatic range in Europe, 155 among 174 exotic plant species absent from the Park were predicted to establish within its boundaries; among these, 40 clonal perennials were considered the highest threat to the Park’s biodiversity. Focusing on smooth brome (Bromus inermis Leyss.), a Eurasian perennial, threatening the structure and function of native prairies throughout the Great Plains, I extended my research to investigate the role of dispersal, establishment, proliferation, and persistence in characterizing its threat to the endemic diversity of northern fescue prairies, protected within Riding Mountain National Park. Patterns of smooth brome invasions were contingent on the type of propagules dispersed. The shallow dispersal gradient of individual florets combined with the steeper gradient of panicles and spikelets suggested that smooth brome is capable of simultaneously invading along dense fronts as well as by establishing isolated foci. While low correlations between the number of dispersed seeds and their recruitment suggested post-dispersal transport, seedling establishment remained contingent on prairie diversity. Seedling biomass increased with declining plant diversity, however, its impact depended on the availability of soil nitrogen. As a result, disturbed areas, preserving the root function of native plants, resisted smooth brome establishment. Even though low nitrogen contributed to a decline in seedling biomass, physiological integration between ramets facilitated their vegetative proliferation in low resource environments. Despite its rapid establishment and proliferation, smooth brome productivity declined at the center of invading clones. Although field and greenhouse observations failed to implicate soilborne pathogens, reasons for the observed decline remain unresolved. My research demonstrates that while Riding Mountain National Park and other natural areas in western Canada will continue to be impacted by exotic plants, integrating key stages in their life history provides an important conceptual framework in predicting their threat to natural areas and prioritizing management.

Invasive exotic species threaten the biodiversity and function of native ecosystems. Existing models, attempting to predict and control successful invaders, often emphasize isolated stages of in their life history and fail to formalize interactions between exotic species and recipient environments. In order to elucidate key mechanisms in the success of select invaders, I investigated the role of dispersal, establishment, proliferation, and persistence in their threat to natural areas. Focusing on Riding Mountain National Park, Manitoba, Canada, I integrated the native climatic range and biological traits of 251 exotic vascular plants reported inside and outside the park. Based on their climatic range in Europe, 155 among 174 exotic plant species absent from the Park were predicted to establish within its boundaries; among these, 40 clonal perennials were considered the highest threat to the Park’s biodiversity. Focusing on smooth brome (Bromus inermis Leyss.), a Eurasian perennial, threatening the structure and function of native prairies throughout the Great Plains, I extended my research to investigate the role of dispersal, establishment, proliferation, and persistence in characterizing its threat to the endemic diversity of northern fescue prairies, protected within Riding Mountain National Park. Patterns of smooth brome invasions were contingent on the type of propagules dispersed. The shallow dispersal gradient of individual florets combined with the steeper gradient of panicles and spikelets suggested that smooth brome is capable of simultaneously invading along dense fronts as well as by establishing isolated foci. While low correlations between the number of dispersed seeds and their recruitment suggested post-dispersal transport, seedling establishment remained contingent on prairie diversity. Seedling biomass increased with declining plant diversity, however, its impact depended on the availability of soil nitrogen. As a result, disturbed areas, preserving the root function of native plants, resisted smooth brome establishment. Even though low nitrogen contributed to a decline in seedling biomass, physiological integration between ramets facilitated their vegetative proliferation in low resource environments. Despite its rapid establishment and proliferation, smooth brome productivity declined at the center of invading clones. Although field and greenhouse observations failed to implicate soilborne pathogens, reasons for the observed decline remain unresolved. My research demonstrates that while Riding Mountain National Park and other natural areas in western Canada will continue to be impacted by exotic plants, integrating key stages in their life history provides an important conceptual framework in predicting their threat to natural areas and prioritizing management.