Product differentiation is a key feature of modern economies. Although its relevance had already been recognized in the XIX century, it is only in the last forty years that a formal treatment has been developed. The 'address approach' distinguishes between horizontal and vertical product differentiation; in the former, consumers do not agree on the quality ranking of commodities, while in the second they do. The first three chapters of this thesis deal with vertical product differentiation in an imperfectly competitive framework. In particular, the first two essays take into account the empirical evidence concerning labor requirements in the production of vertically differentiated goods in order to model labor and product markets in an upstream-downstream relation to each other. The main assumption is that higher variants of vertically differentiated commodities require highly-skilled labor. This allows to study the links between labor markets and vertically differentiated products markets, their equilibrium implications and issues of trade liberalization. The third chapter explores another side of vertical product differentiation, namely the time-to-market of vertically differentiated goods. This interval, which corresponds to the lapse of time for a product to reach the market, is studied under the assumption that firms can make it shorter through costly investments. The analysis compares firms' choices as a function of the parameters characterizing products and technologies and of market structure. The last chapter develops a general equilibrium model with imperfect competition. The concept of monopoly equilibrium is applied to a Ricardian economy in order to study the emergence of trade in that framework.

Product differentiation is a key feature of modern economies. Although its relevance had already been recognized in the XIX century, it is only in the last forty years that a formal treatment has been developed. The 'address approach' distinguishes between horizontal and vertical product differentiation; in the former, consumers do not agree on the quality ranking of commodities, while in the second they do. The first three chapters of this thesis deal with vertical product differentiation in an imperfectly competitive framework. In particular, the first two essays take into account the empirical evidence concerning labor requirements in the production of vertically differentiated goods in order to model labor and product markets in an upstream-downstream relation to each other. The main assumption is that higher variants of vertically differentiated commodities require highly-skilled labor. This allows to study the links between labor markets and vertically differentiated products markets, their equilibrium implications and issues of trade liberalization. The third chapter explores another side of vertical product differentiation, namely the time-to-market of vertically differentiated goods. This interval, which corresponds to the lapse of time for a product to reach the market, is studied under the assumption that firms can make it shorter through costly investments. The analysis compares firms' choices as a function of the parameters characterizing products and technologies and of market structure. The last chapter develops a general equilibrium model with imperfect competition. The concept of monopoly equilibrium is applied to a Ricardian economy in order to study the emergence of trade in that framework.

This paper presents an example of price discrimination on the market for marijuana in northern Bohemia in 2006. First, a model for a multifirm market is built, with emphasis on the existence of two types of firms and two qualities good offered. It is shown that in the case of a dealer of two qualities of marijuana there is an incentive to raise the price of the more expensive quality and reduce the price of the cheaper. Using econometric estimates, price discrimination is found in accordance with the predictions of the model in the amount of about 50 crowns per gram.

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<p>The ability to digitize information goods such as music and movies and the growing accessibility of the Internet has led to online piracy and the emergence of a new class of retailers that specialize in digital downloads. Both online piracy and digital retailers have changed the dynamics of the information goods distribution channel. In my dissertation I focus on issues related to this change.</p><p>In the first chapter, "Digital music set free: the flip side of DRM," I study the effect of Digital Rights Management (DRM) mechanisms on the competition between traditional and digital retailers and on online piracy. DRM refers to technologies designed to control how end users may access, copy, or convert digital media. In the context of music downloads, DRM makes piracy of digital music more difficult, and until recently, most legal outlets for downloadable music only sold songs with DRM protection. Recently download retailers have convinced record companies to allow them to sell DRM-free music. The introduction of DRM-free music raises several important questions: Will music piracy increase as the opponents of DRM-free music predict? Will the music industry profits go up or down? How will CD retailers be affected? Will all labels start selling the unprotected (DRM-free) content? </p><p>I address these and related questions by developing a model of a music distribution channel that allows a record label to sell through both traditional CD retailers and iTunes-like download services at different wholesale prices. Among the interesting results, the analysis indicates that the level of piracy may decline when DRM protection is removed and that the traditional retailers much prefer to compete with distributors of pirated digital music rather than with legal music download services.</p><p>The competition between online and traditional retailers has led to interesting pricing policies on which I focus in the second chapter, "Digital movies at one simple price: the effect on competition." Online retailers tend to prefer uniform pricing (e.g. iTunes Store) where all "products" carry a single price, while traditional retailers do not have a policy of uniform prices. It is important to understand why one retailer should choose a single, uniform price and what impact it has on the competing retailer who chooses multiple prices. I focus specifically on the impact that single price policy adopted by digital retailer has on the traditional retailer. I also analyze the choice of uniform vs. differentiated pricing by modeling the competition between online and traditional retailers for vertically differentiated information goods. Importantly, I demonstrate how the asymmetric equilibrium we observe in the market today can change systematically with the nature of competition between the retailers.</p> / Dissertation

We study the optimal resource portfolio for a price-setter firm under a consumer choice model with supply and demand risks. The firm sells two products that are vertically differentiated, and has the option to invest in both dedicated and flexible resources. Our objective is to understand the effectiveness of the two hedging mechanisms, resource flexibility and demand management through production differentiation, under demand and supply risks. We show that the presence of consumer-driven substitution does not always reduce the need for the firm to offer differentiated products. In particular, when the firm faces demand risk and differential production costs, it might invest in the flexible resource and offer differentiated products for a wider range of parameters. Interestingly, more uncertainty (in the form of additional supply risk) does not always make the firm more eager to adopt a hedging mechanism. This depends on the relationship between resource risks, product attributes, and resource investment costs. On the other hand, when the firm invests in the flexible resource, this never completely replaces the dedicated resources, and always results in a "diverse" resource portfolio. While this happens in the supply risk setting mainly due to resource diversification advantage, it also happens in the demand risk setting due to the vertical differentiation between the products. Finally, in the absence of differential production costs, demand management by itself (without resource flexibility) becomes powerful enough to hedge against the demand risk, but not the supply risk, due to the additional resource diversification benefit of the flexible resource in the latter setting. / Ph. D.

八十年代，隨著總體經濟的失衡，國內之出口結構也起了重大的變化；值得注意的是中間產品以及機器設備比重的增加，以及非耐久消費財比重的減少。本研究的研究對象為民國七十年到八十二年我國製造業的出口情形，觀察出口結構與出口品質的變化，根據Falvey(1981)與Flam & Helpman(1987)建立實證模型，分別估計這些模型並進行Non-nested之假設。本研究的結論如下：一、在出口結構方面高勞動密集財之出口有逐年下降之趨勢，而高資本與高技術密集財則有逐年上升之趨勢，顯示我國之出口結構已慢慢轉向資本與技術密集。二、出口結構之決定因素勞動密集財出口比例之變化與國內要素稟賦，如固定資本、人力資本以及勞動的關係較為密切；資本密集財的出口因素用Ricardian理論或H-O理論來解釋都不是很完全；而技術密集財的出口決定因素則與相對成本和技術變動的關係較為密切，這些我國出口情形的實證結果與過去之文獻結果恰可以相呼應。三、在出口品質方面我國製造業的出口品質有逐年上升的趨勢，其主要決定因素為相對勞動成本之上升，以及技術之變動，而與要素稟賦之關係較不密切。

This dissertation explores several aspects of the theory in industrial organization. The first chapter builds a model with two cost asymmetric firms who not only have Cournot competition in the spot market but also have the opportunity to trade forward contracts. It is shown that with forward trading, low cost firm not always produces more than high cost firm. In an interior equilibrium, both total output and consumer welfare increase compared to the case without forward trading. When cost function is linear, forward trading is socially beneficial in that low cost firm has higher market share as well as profit share, and that total output, consumer welfare and social welfare increase. The second chapter analyzes duopoly firms' choices among ad-free and ad-supported service with different advertising displays: mandatory advertising where ads are integrated with the main content and cannot be dismissed by users; or optional advertising where users are allowed to dismiss ads at will. The model also takes into account the effect of consumers' heterogeneous ad tastes on their contribution to ad revenues. The results reveal that ad revenues intensify competition, suppress equilibrium prices and profits, and diminish the differentiation effect. The third chapter studies firms' business model choices and pricing decisions when they can choose to provide ad-free service, ad-supported service with cost-per-click (CPC) revenue model or cost-per-mille (CPM) revenue model, or a combination of them in monopoly or duopoly environment. It's shown that offering both types of ad-supported services is not an optimal strategy for a monopolist and that its optimal strategy is to vertically differentiate by providing an ad-supported service and an ad-free service. Furthermore, when the monopolist adopts the CPM-based ad revenue model, the price of the ad-supported service is more sensitive to increases in the marginal ad revenue than the case with the CPC-based model. In the equilibrium of competitive setting, exactly one firm offers an ad-supported service alone while the other firm offers the ad-free service with or without the same type of ad-supported service depending on the ad revenues. / text

Dans la première partie, nous considérons une relation positive entre la qualification des travailleurs et la qualité du produit final, dans un modèle d’équilibre partiel avec un marché verticalement différencié. Nous prouvons qu’avec l’introduction du marché du travail, le résultat standard de différenciation en qualités n’est plus vérifié. Nous testons ce résultat en ouvrant l’économie à l’international. Nous considérons ensuite un modèle d’équilibre général où les individus sont potentiellement consommateurs, travailleurs et propriétaires des firmes. Nous nous intéressons à la préférence de la majorité entre le monopole et le duopole. Nous montrons que ce choix démocratique ne génère pas nécessairement moins de pauvreté sur le plan individuel et collectif. Dans la deuxième partie, nous introduisons des universités en amont du marché du travail. Dans un premier temps, nous montrons que pour un niveau d’inefficience faible de l’Etat, la privatisation partielle apparaît à l’équilibre et l’Etat est généralement largement majoritaire. Ensuite, nous nous intéressons au financement de l’éducation. Nous déterminons le niveau des frais d’inscription publics à travers un vote à la majorité, dans un système éducatif mixte. Nous prouvons que les extrêmes ou la classe moyenne sont majoritaires selon le niveau du coût marginal de la qualité privée. Finalement, nous nous intéressons au sponsoring des universités par les firmes. Moyennant un modèle d’agence commune, nous prouvons qu’il existe une relation négative entre la proportion des travailleurs qualifiés et la part des firmes dans le financement de l’éducation. / We consider, first, a positive relationship between workers’ skills and product quality, in a model of partial equilibrium with vertical preferences. We prove that the standard result of vertical differentiation no longer applies by the introduction of the labor market. We also test the robustness of our results under globalization. Then, we consider a general equilibrium model where individuals are potentially consumers, workers and shareholders. We study the majority preference between duopoly and monopoly, and we prove that the democratic choice doesn’t always generate less poverty, collectively and individually. Second, we introduce universities upstream the labor market. We prove that partial privatization of the university appears at equilibrium for a low level of public inefficiency, where the State has a broad majority. Then, we study the question of financing education. We determine the level of public tuition fees via a majority voting model, in a mixed education system. We prove that the extremes or the middle class hold the majority depending on the marginal cost structure of the private quality. And finally, we study firms’ sponsoring universities. Using a common agency approach, we prove that there is a negative relationship between the proportion of skilled workers and the share of firms in financing education.

Diese Dissertation setzt sich aus fünf Forschungspapieren zusammen. Jedes Kapitel enthält ein Papier. Das erste Kapitel untersucht den Zusammenhang zwischen der Größe des Kundenstamms einer Firma und ihrem Gewinn in einem Markt mit Wechselkosten. Entgegen unserer Intuition wird gezeigt, dass Firmen nicht immer von einer Vergrößerung ihres Kundenstamms profitieren, weil diese die Intensität des Wettbewerbs beeinflusst. Kapitel 2 führt eine ähnliche Untersuchung durch, aber für einen Markt, in dem die Konsumenten unvollständig über die Standorte der Anbieter informiert sind. Es zeigt sich auch hier, dass eine Firma nicht immer von einem großen Kundenstamm profitiert. Die zugrunde liegenden Mechanismen unterscheiden sich jedoch deutlich von denen in Kapitel 1. Kapitel 3 ist eine Erweiterung des Modells mit unvollständiger Konsumenteninformation hin zu einer vollständig dynamischen Version. Im Zentrum der Analyse stehen nun die dynamischen Eigenschaften des Modells. Unter den Annahmen über die graduelle Verbreitung von Information auf der Konsumentenseite entsteht Trägheit in den Marktanteilen der Firmen. Dynamik entsteht im Modell ausschließlich aufgrund der Verwendung von gemischten Preisstrategien. Kapitel 4 analysiert Wettbewerb in einem vertikal differenzierten Markt. Hier gibt es keine Trägheit auf der Nachfrageseite. Das Hauptergebnis der Analyse ist, dass Wohlfahrtsverluste, die im Duopol aus ineffizienter Qualitätswahl resultieren, in Märkten mit drei oder mehr Wettbewerbern fast vollständig verschwinden. Dieses überraschende Ergebnis resultiert aus einem Regimewechsel in der Art des Wettbewerbs, der beim Übergang vom Duopol zum Markt mit drei Wettbewerbern auftritt. Kapitel 5 ist eine Erweiterung von Kapitel 4. Während in Kapitel 4 ein quadratischer Zusammenhang zwischen Kosten bzw. Zahlungsbereitschaft und Qualität angenommen wurde, wird die Analyse nun für eine allgemeinere nicht-lineare Abhängigkeit durchgeführt. Es werden grundlegende Einsichten über das Funktionieren von vertikal differenzierten Märkten vermittelt. So zeigt sich, dass der allgemein postulierte Vorteil der Firma mit der höheren Produktqualität nicht allgemeingültig ist. Ob dieser besteht, hängt von der Art der strategischen Interaktion ab. / This dissertation consists of five independent research papers. Each chapter represents one paper. The first chapter analyzes the shape of the relation between the size of a firm’s customer base and profit in a market with consumer switching costs. Contrary to common wisdom, it is shown that a firm is not automatically better off with a larger customer base, as the size of its customer base affects the intensity of price competition. Chapter 2 performs a similar exercise, but for a market where consumers are not fully informed about the locations of the different suppliers. Once more, it is shown that firms do not always benefit from an increase in the size of their customer base. However, the underlying mechanisms are rather different than in the model with switching costs. Chapter 3 is an extension of the model introduced in chapter 2 to a fully dynamic game. The focus of chapter 3 is on the dynamics in a market with incomplete consumer information. Under the assumptions about the gradual diffusion of information among consumers, there is inertia in the market shares. Dynamics are generated solely by the firms’ usage of mixed pricing strategies. Chapter 4 analyzes competition in a vertically differentiated market. There is no inertia on the demand side. The main result of the analysis is, that welfare losses that stem from an inefficient choice of qualities in the duopoly case, disappear almost completely as soon as three or more competitors are in the market. This surprising result is related to a regime change in the nature of competition that occurs at the transition from duopoly to triopoly. Chapter 5 is an extension of chapter 4. Whereas the model introduced in chapter 4 was based on a quadratic relation between costs or willingness-to-pay and quality, the analysis is now extended to a more general non-linear dependency. The analysis provides fundamental insights into the functioning of vertically differentiated markets. Interestingly, the well-known high-quality advantage is not a robust feature of these markets. Whether it is obtained, depends on the nature of strategic interaction between the firms.