The thesis consists of four papers. The first two essays deal with entry externalities, the third studies the Law of One Price (LOP), while the last essay examines average profits for a monopolist under uncertainty. In the first essay, entry externalities in the form of information and positive payoff externalities are studied. When a firm enters a market, it often imposes externalities on existing firms and/or future potential entrants. If products are substitutes, these externalities are typically negative; if products are complements, the externalities are typically positive. Externalities related to substitution or complementarities between products are called payoff externalities, since entry by one firm has a direct effect on the other firms' payoff. Another type of externality arises when firms have private information about the profitability of entry. In this case, the entry decision of one firm potentially reveals that firm's private information. The focus of the paper is on the scope for intervention for an uninformed social planner, when firms privately know the profitability of entry and moreover, the firms have an option to delay their entry. The main result is that there is insufficient entry, since firms delay too much in equilibrium and further, the social planner can increase welfare by subsidizing early entry. Continuing on this theme, the second essay has the same focus, but instead takes the time of entry as fixed, while generalizing the analysis of payoff externalities also to the case of negative payoff externalities. The main contribution is the characterization of equilibria under both positive and negative payoff externalities and the implications for public policy. Here, the scope for intervention will, in contrast to the results in the first essay, be low, when entry is profitable for uninformed firms. In the third essay (joint with Richard Friberg), deviations from the LOP are studied in the presence of transport costs, under the assumption that firms can endogenously choose to segment markets in order to prevent arbitrage by consumers. It is shown that the deviation from LOP can increase as transport costs fall between countries. The last essay (joint with Richard Friberg), studies the problem facing a monopolist when the cost of inputs is uncertain. The main result is that the monopolist can gain from this uncertainty, in the sense that average profits are increasing in the variability of costs. / Diss. Stockholm : Handelshögsk., 2001

Apresentamos três estudos sobre os assuntos mencionados no título. O primeiro, econométrico, avalia os impactos da quebra de exclusividade no lado credenciador da indústria de cartões de pagamentos no Brasil que ocorreu em 2010. Por um lado, tentamos a construção de um grupo de controle e, por outro, fazemos a decomposição dos preços em markup e custo marginal. As estimações, que empregam um banco de dados com informações individuais para os maiores lojistas de cada setor, apontam para o sucesso dessa intervenção na promoção da concorrência. No segundo artigo, propomos que cobranças indevidas feitas por instituições financeiras podem ser uma forma de discriminação de preços, já que sua devolução demanda esforço dos consumidores. Nesse caso, tendo em vista que as cobranças indevidas ótimas dependem do perfil do consumidor, construímos um teste baseado numa função de verossimilhança para mostrar como a informação de reclamações poderia ser utilizada para detectar esse tipo de comportamento, mesmo quando a autoridade interessada nesse monitoramento sabe menos sobre os clientes que a instituição financeira. O terceiro artigo, teórico aplicado, estuda o comportamento de plataformas comerciais em mercados de dois lados nos quais os papéis de compradores e vendedores são bem definidos e há heterogeneidade dentro de cada um desses grupos de agentes. Diferentemente do que ocorre no caso em que os interesses são simétricos, no lado vendedor não ocorre autosseleção dos participantes e a plataforma passa a ter um papel de certificação dos vendedores, criando ambientes de qualidade selecionada onde um preço maior pode ser cobrado dos compradores. / This thesis has three papers related to the subject in the title. The first one, an econometric paper, evaluates the impact of a break of exclusivity promoted by Brazilian authorities in the payment card acquiring industry in 2010. We use two frameworks: in one of them, we try to identify categories of merchants to use as control group, while in the other we decompose prices into markup and marginal cost elements. The estimations employ a dataset of individual merchants with information for the largest ones in each category. The results indicate success in promoting some competition. In the second paper, we argue that undue charges made by financial institutions may be a form of price discrimination, since their reversion requires effort from consumers. Given that in such case the optimal undue charges depend on consumers profiles, we build a likelihood function based test to show how information on complaints might be used to detect this sort of behavior, even when the relevant authority knows less about clients than the financial institution. The third one, an applied theoretical paper, analyses the behavior of commercial platforms in two-sided markets where the roles of buyers and sellers are well defined and there is heterogeneity within each of these groups of agents. Differently from what happens in a setting with symmetric interests, in the seller side no self-selection takes place and the platform gains an important quality certification role, creating spaces for trade where seller quality is higher and buyers are willing to pay more.

Les notions de plateforme, de marché bifaces ou même multi-faces sont aujourd’hui au cœur des discussions économiques du fait de l’explosion du e-commerce lié à l’essor des nouvelles technologies de l’information. Ces plateformes en lignes offrent de nouvelles opportunités et soulèvent de nombreuses questions (stratégie tarifaire, règlementation, etc.). Les deux premiers chapitres de cette thèse s’intéressent aux plateformes de réservation en ligne et plus particulièrement à l’impact concurrentiel des clauses de parités tarifaire. Ces dernières, mises en place par les plateformes, imposent aux vendeurs de proposer son bien ou service via la plateforme au meilleur prix disponible sur tous les autres canaux de ventes. Dans le premier chapitre, je montre que, d'un point de vue théorique, l'effet concurrentiel des clauses de parité est majoritairement négatif mais peut devenir positif en fonction du pouvoir de négociation de chacun des acteurs. Dans un second temps, une analyse empirique reposant sur une base de données unique de plus de 6 millions de prix, me permet de montrer que la suppression des clauses de parité à Paris a engendré une baisse tarifaire moyenne des hôtels de -3,1% à - 4,5%. Cette baisse peut en partie s'expliquer par une augmentation des stratégies de discrimination tarifaire. En effet, les hôtels ont augmenté de 1,4 à 2,3% la discrimination entre plateformes et ils ont augmenté de 2,1% à 3,6% leurs stratégies de discrimination inter-temporelle. Le dernier chapitre de cette thèse est dédié à l'analyse des amendes décidées par l'Autorité de la Concurrence entre 2006 et 2018 pour des pratiques de cartels. Nous montrons que ces amendes sont sous optimales car elles ne satisfassent pas les critères de dissuasion et de compensation. / The Internet technology and the web economy create new types of markets and new relationships between market players. The majority of these new markets can be associated to platforms where two or more sides of the same market meet. Such “multi-sided” industries raise specific issues. Determining the optimal pricing strategy for both the platform and the users selling goods through the platform is one of the main challenges of this new economy. The first two chapters of my thesis analysis Price Parity Agreement (PPA) from a theoretical and an empirical point of view. I first study the effect of Price Parity Agreements from a theoretical perspective. I demonstrate that PPAs on the online booking market are detrimental to consumers if platforms have most of the bargaining power. They attenuate competition between platforms, lead to higher commission fees and higher hotel rooms’ prices. However, MFN clauses may also be welfare improving when hotels own the bargaining power and competition between them is high. The second chapter is dedicated to an empirical analysis of the effects of PPAs. Using a before-after design and controlling for external shocks, I demonstrate that the end of Price Parity Agreements imposed by public authorities to OTAs causes a decrease of about 3.1% to 4.5% in the average level of prices set by hotels. This decrease may be explained by an increase of price discrimination. I show that the level of price discrimination across OTAs increases by 2.3% to 1.4% after the drop of Price Parity Agreements and that the degree of inter-temporal price discrimination also increases by 3.6% to 2.1%. The last chapter of my thesis is focused on the analysis of the financial fines imposed by the French Autorité de la Concurrence to cartels in France between 2006 and 2018. We show that the level of these fines is sub-optimal and doesn’t meet the deterrence objective in the majority of the cases.

LLM / Department of Mercantile Law / The study critically analyses the concurrent enforceability of restraint of trade and garden leave in South African Labour law. The study seeks to answer the question of whether or not the simultaneous enforceability of restraint of trade agreements and garden leave is reasonable. Designed within a qualitative paradigm primarily based on a critical literature review, the study employs a doctrinal approach to establish the contemporary legal position in respect of the simultaneous enforceability of restraint of trade agreements and garden leave in South African Labour law. The objectives pursued by the study are to mitigate the controversies and clear the confusion relating to the enforceability of restraint of trade agreements; to justify the doctrine of restraint of trade; assess the reasonableness of the simultaneous enforceability of garden leave and restraint of trade; examine the onus of proof in matters dealing with the enforceability of restraint of trade agreements; test the constitutionality of restraint of trade agreements; evaluate the relationship between restraint of trade agreements and garden leave; and propose practical recommendations that can be employed to address identified legal flaws in the context of the topic. Structurally, the study begins with unpacking the background to the research topic, the history, origin and rationality of restraint of trade agreements together with an assessment of their enforceability. It further examines the effect of garden leave on restraint of trade agreements, outlines comparative perspectives on restraint of trade, including aspects relating to garden leave and highlights lessons South Africa may learn from the selected jurisdictions. Finally, the study recommends that South African jurisprudence should be developed to shift the burden of proof to employers to prove reasonableness of garden leave and restraint of trade agreements, to impose an obligation on employers to pay former employees for rendering them jobless and to set a maximum period that an employee can be prevented to compete or be employed by employer’s competitors. / NRF

<p>The dissertation is consisted of two essays on Affordable Care Act Marketplace plan pricing. These two essays are the two chapters of the dissertation respectively.  </p> <p>First essay studies the effect of Medicaid expansion on ACA Marketplace plan premium. The Affordable Care Act (ACA) aims to mitigate Americans’ uninsured crisis by expanding Medicaid and establishing the ACA Marketplace. The Medicaid expansion has a profound impact on Marketplace plan premiums. On the one hand, it lowers the premiums because the expansion drives out the people with lower income from Marketplace plans, resulting in a pool with a lower risk score for these plans. On the other hand, the Medicaid expansion may shrink the pool size of Marketplace plans, resulting in a riskier pool and a higher Marketplace plan premium. Integrating data from multiple sources, we study how these two competing effects vary across markets with different demographics. We find that the premium-reduction effect is less pronounced in more wealthy markets, while the premium-increase effect is less pronounced in more populous markets. We further find that the Medicaid expansion overall decreased the Marketplace premiums, with more reduction for Silver plans than Bronze plans. We also explore how the Medicaid expansion can lower Marketplace premiums indirectly through the change of the market structure. We finally show the heterogeneity of the net impact of the Medicaid expansion on Marketplace premiums across markets. Our results offer important policy and managerial implications.</p> <p>The second essay explores the effect of insurer competition on marketplace plan premiums. ACA Marketplace is a new market opportunity for insurers that grant them access to a new group of customers who were not insured before. Previous studies utilize ACA marketplace data and find that additional insurers on the market are associated with a premium decrease in Marketplaces for a benchmark plan. However, the impact of the insurer entry on the premium is not the same for all plans. Using data from 2014 to 2017, we empirically examine the effect of insurer entry on the premium on Marketplace. Our study first confirms the finding that the premium of the second-lowest Silver plans decreases in the number of insurers. We further find evidence of different price trends across plans of different quality levels with additional insurers on the market. When more insurers are on the market, the premium increases for higher-end plans and decreases for lower-end plans. Our analysis shows that intensified competition may exaggerate price discrimination in certain segments while alleviate price discrimination in other markets. The results offer important managerial implications. </p>

This thesis examines the microeconomic consequences of the arrival of open source in the software market. Specifically, it analyzes three features of open source software by using specific models of industrial organization. Open source software is free, and may be modified or duplicated by anyone. The first paper studies the entry of an open source software in a closed source software market. Using a model of horizontal differentiation, the analysis considers a closed source firm's investment in the quality of its software. The introduction of open source on the market reduces the firm's investment in quality and increases the price of its software. Moreover, the entry of open source software may reduce consumer welfare. Post-entry by an open source software, the reduction in market share lowers the firm's incentive to invest in quality. The second paper features vertical differentiation to study a monopolist selling supporting product to its software. The study begins by contrasting the supply of support by an open source provider and a closed source vendor. The model shows that in both cases the levels of support offered are the same. In addition, consumer welfare is higher and profit lower under an open source software. Then, the paper considers the competition in the provision of support. Here, the supply of high level support is greater than under a monopolist. Finally, the monopolist adopts a dual licensing strategy to extract more surplus from developers interested in modifying open source software and redistributing the resulting product. This technique, when the developers place high value on the source code, generates more profit if the monopolist chooses to publish as open source rather than closed source. The last paper studies how a closed source firm is affected by the introduction of an open source benefiting from contributions by users. A vertical differentiation model is used, and reveals that, when contribution of users is present, the closed source vendor may lower its price to a level where it forces the open source out of the market. The firm's lower price not only increases demand for its software, but also induces consumers into switching from open to closed source software therefore reducing the contribution of users. / Les logiciels libres sont uniques en leur genre\ : non seulement sont-ils distribués gra-tuitement, mais on peut aussi les modifier et les copier. Cette thèse étudie l'impact de ces propriétés du logiciel libre sur la compétition et sur les entreprises de logiciel propriétaire. Des modèles propres à l'organisation industrielle sont utilisés. Le première étude examine l'arrivée d'un logiciel libre sur un marché occupé par un logiciel propriétaire. En utilisant un modèle de différenciation horizontale, le papier consi-dère une firme propriétaire qui investit dans la qualité de son logiciel. L'arrivée d'un logiciel libre cause l'entreprise du logiciel propriétaire à réduire le niveau de son investissement et à augmenter le prix de son produit. Il s'avère alors que l'introduction du logiciel libre sur le marché réduit l'investissement de l'entreprise et engendre même l'augmentation du prix du produit. De plus, l'arrivée du logiciel libre peut réduire le niveau de bien-être des consommateurs. Comme le logiciel libre ne réagit pas aux décisions stratégique de l'entreprise, cette dernière voit son marché réduit peu importe sa stratégie. La firme décide conséquemment de vendre un produit de moindre qualité à un prix plus élevé à une clientèle réduite. Le deuxième papier propose un modèle qui utilise la différenciation verticale afin d'exa-miner un monopoleur offrant un produit complémentaire à son logiciel. L'étude compare d'abord les cas d'un logiciel libre et d'un logiciel propriétaire, toujours dans le contexte d'un monopoleur offrant du support professionnel pour son logiciel. Il est établi que le bien-être des consommateurs est plus élevé, et le profit inférieur dans le cas d'un distributeur de logiciel libre. Ensuite, le modèle initial est modifié avec l'ajout d'une seconde entreprise offrant du support professionnel. Dans ce cas, l'offre de support de haut niveau est plus élevée. Finalement, le monopoleur adopte une stratégie de licences doubles. Ce concept permet au monopoleur de proposer la vente d'une licence même si son logiciel est libre. Cette technique génère plus de profits, certaines conditions étant présentes, que si l'entreprise optait pour un logiciel propriétaire. Un logiciel libre profite des contributions de ses usagers pour améliorer son produit. Le troisième papier examine l'arrivée d'un tel produit sur un marché dominé par un logiciel propriétaire. Le modèle de différenciation verticale utilisé contraste les deux logiciels dans un marché donné et révèle que la contribution des utilisateurs peut diminuer la part de marché du logiciel libre au profit de son conccurrent. De fait, en diminuant ses prix le licenceur du logiciel propriétaire incite le consommateur à délaisser le logiciel libre pour le produit de son concurrent.

Diese Dissertation besteht aus drei unabhängigen Kapiteln in Vertragstheorie und Industrieökonomik. Die Kapitel 1 und 2 bearbeiten Fragestellungen der Vertragstheorie. In diesen Kapiteln studiere ich die Ausprägung der Informationsasymmetrien, die in vertraglichen Beziehungen entstehen, wenn die schlechter informierte Partei versucht ihren Informationsnachteil gegenüber dem Vertragspartner zu reduzieren. In Kapitel 1 analysiere ich die Möglichkeit, dass die schlechter informierte Vertragspartei eine dritte Partei – einen Berater oder Supervisor – konsultiert, der jedoch mit der besser informierten Partei kolludieren könnte. In Kapitel 2 analysiere ich den Fall, in dem die schlechter informierte Vertragspartei selbst Monitoring-Aktivitäten aufnehmen kann, um zusätzliche Information zu sammeln. In Kapitel 3 untersuche ich den Effekt von Informationsasymmetrien innerhalb von Unternehmen auf diskriminierende Preissetzungsstrategien in Zwischengutmärkten. Hierbei analysiere ich Preisdiskriminierung und die aus dieser resultierenden Wohlfahrtseffekte in einem Modell eines Zwischengutmarktes, auf dem ein monopolistischer Verkäufer ein Zwischengut an zwei Abnehmer verkauft, die aufgrund ihrer unterschiedlichen vertikalen Organisation unterschiedlich stark von Agenturkosten betroffen sind. / This dissertation consists of three independent chapters in the fields of contract theory and industrial organization. Chapters 1 and 2 are concerned with topics in contract theory. In these chapters, I study the form of information asymmetry that arises in contractual relationships where the less knowledgeable party can reduce its informational disadvantage vis-à-vis the contractual partner. In Chapter 1, I analyze the opportunity of the less knowledgeable party to consult a third party – an expert or supervisor – who can provide advice. In Chapter 2, the less knowledgeable party can itself engage in monitoring activities to gather additional information. In Chapter 3, I explore the effect of information asymmetry within firms on discriminatory pricing in intermediate good markets. In particular, I study price discrimination and the associated welfare effects in an intermediate good market where a monopolistic upstream firms sells an input to downstream firms that vary in their exposure to the problem of asymmetric information due to different degrees of vertical integration.

O presente trabalho estuda a vedação da discriminação de preço nas redes contratuais de distribuição, tanto pelo aspecto concorrencial, quanto pelo aspecto civil. A abordagem concorrencial decorre da existência de um ilícito assim tipificado na Lei Antitruste brasileira. É preciso identificar os requisitos de aplicação próprios do direito concorrencial, que tem como bem jurídico tutelado a defesa da concorrência. Fez-se um estudo de direito comparado com o direito concorrencial norte-americano, em que vigente o Robison-Patman Act. A abordagem de direito civil-contratual depende da identificação dogmática da existência de uma rede contratual, a partir da verificação da finalidade econômica global em um dos elementos essenciais dos contratos individuais que formam a rede. Necessário, ainda, proceder à qualificação jurídica dos contratos de distribuição, partindo da sua causa e dos demais elementos estruturais que informam se tratar de um contrato atípico. A vedação à discriminação decorre da incidência da cláusula geral do art. 187 do CC/02, que proíbe o abuso do direito em razão de um exercício que exceda manifestamente os limites impostos pelos dois critérios trabalhados: a finalidade econômica ou social do direito e a boa-fé. Distingue-se a boa-fé enquanto criadora de deveres laterais de conduta da confiança enquanto protetora de uma situação de confiança. A vedação à discriminação de preço decorre do standard de boa-fé na função de criadora de deveres de conduta para o organizador da rede diante dos distribuidores que lhe estejam vinculados nessa rede contratual. O referencial valorativo é a lealdade que se espera do organizador da rede nesse contexto negocial. Estuda-se os diversos critérios econômicos justificativos do que seja uma justa e leal diferenciação de preço sob o influxo do conceito operativo de igualdade elaborado no âmbito do direito público. / This paper studies the prohibition of price discrimination in contractual networks of distribution, both by the competitive aspect, as the civil aspect. The competitive approach stems from the existence of an unlawful this way typified in Brazilian Antitrust Law. One need to identify the requirements for application of competition law, which legal interest is to protect competition, not competitors. There is a comparative study with the U.S. competition law, because of the current rules of Robinson-Patman Act. The approach of civil-contract law depends on the identification of a network contract from the scanning of the global economic interest in one of the essential elements of individual contracts that compose the network. Also necessary to proceed with the legal classification of the distribution contracts, from his structural and functional (“consideration”) elements that informs it as an atypical contract. The prohibition of discrimination price arises from the general clause of art. 187 of the Civil Code of 2002, which prohibits the abuse of rights in respect of an exercise that clearly exceed the limits imposed by the two criteria worked: the economic or social purpose of the right and good faith. It is distinguished the good faith in its function of create duties of the confidence of a trust situation. The prohibition of price discrimination stems from the standard of good faith in its function of create duties of conduct to the organizer of the network of distributors. The reference value is the loyalty expected of the organizaer of the network in this negotiating context. We study the different economic criteria to be evidence of an equitable and fair price differentiation under the influence of the operating concept of equality established under public law.

This dissertation investigates the relationship of competition and firms' price responses, by analyzing: i) whether new entry reduces price discrimination, ii) when incumbents reduce price discrimination preemptively in response to the threat of entry, and iii) how competition increases prices. The dissertation consists of three independent essays addressing each of the above questions. The first two essays present an empirical analysis of the airline industry and the third essay presents a theoretical analysis of the credit card industry. In the empirical study of the relationship between competition and firms' pricing in the airline industry, I emphasize the importance of distinguishing the equilibrium behaviors with respect to different market characteristics. Major airlines can price discriminate differently in a market where they compete with low-cost carriers comparing to in another market where they don't, and also they can respond dfferently to the threat of entry depending on whether they are certain about the rival's future entry. The study reveals that competition has a positive effect on price discrimination in the routes where major airlines compete against one anther. In these routes, competition reduces lower-end prices to a greater extent than upper-end prices. In contrast, an entry by low-cost carriers results in a significant negative relationship between competition and price discrimination. Thus, the opposite results in the literature are both evident in the airline industry, and it is very important to identify the different forces of competition on price discrimination. Firms can respond to potential competition as well as actual competition. So, I extend the study to the relationship of potential competition and price discrimination, specially in cases where major airlines compete against one another while facing Southwest's threat of entry. I also attempt to suggest major airlines' motives of reducing price discrimination preemptively. The results of the study suggest that incumbents reduce price dispersion when it is possible to deter the rival's entry and that the potential rival discourages incumbents from deterring entry by announcing before its beginning service. Finally, I examine when competition can increase prices in a market, by analyzing the issuing side of the credit card industry. This industry is characterized by a two-sided market with a platform. Under the no-surcharge rule that restricts merchants to set the same price for cash and card purchases, the equilibrium interchange fee increases with competition. This occurs because issuers can compensate losses from competing on the issuing side by collectively increasing the interchange fee. As a result, limiting competition may improve social welfare when the interchange fee is higher than the social optimal level. In contrast, in the absence of the no-surcharge rule, the analysis shows that competition always improves social welfare by lowering the price of the market.

This thesis examines the microeconomic consequences of the arrival of open source in the software market. Specifically, it analyzes three features of open source software by using specific models of industrial organization. Open source software is free, and may be modified or duplicated by anyone. The first paper studies the entry of an open source software in a closed source software market. Using a model of horizontal differentiation, the analysis considers a closed source firm's investment in the quality of its software. The introduction of open source on the market reduces the firm's investment in quality and increases the price of its software. Moreover, the entry of open source software may reduce consumer welfare. Post-entry by an open source software, the reduction in market share lowers the firm's incentive to invest in quality. The second paper features vertical differentiation to study a monopolist selling supporting product to its software. The study begins by contrasting the supply of support by an open source provider and a closed source vendor. The model shows that in both cases the levels of support offered are the same. In addition, consumer welfare is higher and profit lower under an open source software. Then, the paper considers the competition in the provision of support. Here, the supply of high level support is greater than under a monopolist. Finally, the monopolist adopts a dual licensing strategy to extract more surplus from developers interested in modifying open source software and redistributing the resulting product. This technique, when the developers place high value on the source code, generates more profit if the monopolist chooses to publish as open source rather than closed source. The last paper studies how a closed source firm is affected by the introduction of an open source benefiting from contributions by users. A vertical differentiation model is used, and reveals that, when contribution of users is present, the closed source vendor may lower its price to a level where it forces the open source out of the market. The firm's lower price not only increases demand for its software, but also induces consumers into switching from open to closed source software therefore reducing the contribution of users. / Les logiciels libres sont uniques en leur genre\ : non seulement sont-ils distribués gra-tuitement, mais on peut aussi les modifier et les copier. Cette thèse étudie l'impact de ces propriétés du logiciel libre sur la compétition et sur les entreprises de logiciel propriétaire. Des modèles propres à l'organisation industrielle sont utilisés. Le première étude examine l'arrivée d'un logiciel libre sur un marché occupé par un logiciel propriétaire. En utilisant un modèle de différenciation horizontale, le papier consi-dère une firme propriétaire qui investit dans la qualité de son logiciel. L'arrivée d'un logiciel libre cause l'entreprise du logiciel propriétaire à réduire le niveau de son investissement et à augmenter le prix de son produit. Il s'avère alors que l'introduction du logiciel libre sur le marché réduit l'investissement de l'entreprise et engendre même l'augmentation du prix du produit. De plus, l'arrivée du logiciel libre peut réduire le niveau de bien-être des consommateurs. Comme le logiciel libre ne réagit pas aux décisions stratégique de l'entreprise, cette dernière voit son marché réduit peu importe sa stratégie. La firme décide conséquemment de vendre un produit de moindre qualité à un prix plus élevé à une clientèle réduite. Le deuxième papier propose un modèle qui utilise la différenciation verticale afin d'exa-miner un monopoleur offrant un produit complémentaire à son logiciel. L'étude compare d'abord les cas d'un logiciel libre et d'un logiciel propriétaire, toujours dans le contexte d'un monopoleur offrant du support professionnel pour son logiciel. Il est établi que le bien-être des consommateurs est plus élevé, et le profit inférieur dans le cas d'un distributeur de logiciel libre. Ensuite, le modèle initial est modifié avec l'ajout d'une seconde entreprise offrant du support professionnel. Dans ce cas, l'offre de support de haut niveau est plus élevée. Finalement, le monopoleur adopte une stratégie de licences doubles. Ce concept permet au monopoleur de proposer la vente d'une licence même si son logiciel est libre. Cette technique génère plus de profits, certaines conditions étant présentes, que si l'entreprise optait pour un logiciel propriétaire. Un logiciel libre profite des contributions de ses usagers pour améliorer son produit. Le troisième papier examine l'arrivée d'un tel produit sur un marché dominé par un logiciel propriétaire. Le modèle de différenciation verticale utilisé contraste les deux logiciels dans un marché donné et révèle que la contribution des utilisateurs peut diminuer la part de marché du logiciel libre au profit de son conccurrent. De fait, en diminuant ses prix le licenceur du logiciel propriétaire incite le consommateur à délaisser le logiciel libre pour le produit de son concurrent.