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.

The paper is concerned with counterparty credit risk management for credit default swaps in the presence of default contagion. In particular, we study the impact of default contagion on credit value adjustments such as the BCCVA (Bilateral Collateralized Credit Value Adjustment) of Brigo et al. 2012 and on the performance of various collateralization strategies. We use the incomplete-information model of Frey and Schmidt (2012) as vehicle for our analysis. We find that taking contagion effects into account is important for the effectiveness of the strategy and we derive refined collateralization strategies to account for contagion effects. (authors' abstract) / Series: Research Report Series / Department of Statistics and Mathematics

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

[pt] Nessa dissertação de mestrado são desenvolvidos dois ensaios nos quais modelos clássicos de interação estratégica são expandidos para investigar relações entre liquidez e informação assimétrica. No primeiro ensaio, o objetivo é investigar a negociação de opções ilíquidas sujeitas a incerteza exógena. Em particular, desenvolve-se um modelo de barganha no qual a incerteza exógena subjacente é melhor prevista pelo comprador e mostra-se que a existência de uma opção de fora para o vendedor permite que este fixe um prazo para o fim da negociação, estratégia que se mostra ser parte do equilíbrio do jogo. Em outras palavras, o vendedor escolhe uma data para exercer sua opção de fora, o que acontece se não houver acordo até esta data. No segundo ensaio, o objetivo é investigar como corridas bancárias do lado do ativo se relacionam a uma fonte externa de liquidez na forma de um mercado secundário de empréstimos bancários. O principal resultado do segundo ensaio é que corridas bancárias no lado do ativo podem contribuir para existência do mercado secundário de empréstimos bancários, pois criam incentivos para a venda de empréstimos bancários, independentemente de informações privadas que o vendedor venha a adquirir. Esse resultado pode ser relevante no contexto de bancos de varejo. / [en] In this master s degree thesis, I present two essays based on classic models of strategic interaction. In both essays, the overarching theme is how liquidity relates to asymmetric information. On the first, the aim is to investigate bargaining over an illiquid option subject to exogenous uncertainty. In particular, I develop a bargaining model in which the underlying uncertainty is better predicted by the buyer and establish that the existence of the seller s exercise option allows deadline strategies that are shown to be part of the equilibrium of such game. In other words, the seller fixes a date to exercise her outside option, provided that the trade does not take place until that time. On the second essay, I seek to investigate how borrower runs relate to external funding thorough a market for bank loans. This essay s conclusion is that borrower runs may be a driver of the originate-to-distribute banking business model, for it induces the sale of loans irrespective of their quality, rendering the market for bank loans information insensitive. This result might be relevant in the context of relationship banking.

Atualmente, uns dos assuntos mais discutidos na medicina quando se trata de erros é a prescrição médica. Estes erros podem causar grandes danos à saúde dos pacientes, e um dos grandes causadores destes erros é a prescrição feita de forma manual, ou seja, de forma escrita manuscrita pelos médicos. Outro problema decorrente é o fato que nos modelos existentes não contemplam todas as informações necessárias para a correta prescrição. A prescrição médica é um documento que deve conter dados do paciente e de seu tratamento, como medicamentos, doses, periodicidade e, entre outras informações. Como na maioria das vezes quem realiza a infusão dos medicamentos nos pacientes não são os mesmos médicos que os prescreveram, a escrita manuscrita pode dificultar a leitura e o entendimento para quem for realizar o procedimento no paciente. Assim, os problemas proporcionados pela prescrição médica manuscrita como a falta de informações, escrita ilegível, rasuras e informações incompletas, podem ocasionar interpretações errôneas por parte dos profissionais de saúde que os leem, provocando sérios prejuízos diretos aos pacientes. Como atualmente é inevitável à introdução da tecnologia da informação (T.I.) na medicina, houve a iniciativa de criar um questionário eletrônico com perguntas sobre quais informações devem contemplar uma prescrição eletrônica, a fim de não haver falta e nem excesso de informações no modelo de prescrição eletrônica evitando possíveis problemas. Foi criado um questionário contendo 24 questões de múltiplas escolhas, com respostas do tipo SIM ou NÃO. Os questionários foram enviados aos associados da Sociedade Brasileira de Oncologia Clínica. Foram 215 questionários respondidos, sendo que das 24 questões 17 tiveram 80% ou mais de respostas sim, onde significa que estas informações devem fazer parte do modelo de prescrição, que foi desenvolvido a partir destas informações. / Nowadays, one of the most discussed subjects in medicine when it comes to errors, is medical prescription. These errors can cause great harm to patients, and one of the great causes of these errors is the prescription made manually, that is, in handwritten by doctors. Another problem is the fact that in the existing models it is not include all the information necessary for the correct prescription. The medical prescription is a document that should contain data about the patient and their treatment, such as medications, doses, periodicity among other information. As most of the time those who infuse the drugs are not the same doctors who prescribed them, handwriting may make it difficult to read and understand for those who perform the procedure. Thus, the problems provided by medical prescription such as lack of information, illegible writing, erasures and incomplete information, can lead to misinterpretations by health professionals who read them, causing serious harm to patients. As it is currently unavoidable the introduction of informatics technology (IT) in medicine, there was the initiative to create an electronic questionnaire with questions about what information should contemplate an electronic prescription. In order to avoid lack or excess of information in the prescription model, avoiding possible problems, a questionnaire containing 24 multiple choice (YES or NO) questions was created. The questionnaires were sent to the members of the Brazilian Society of Clinical Oncology. There were 215 questionnaires answered, and of the 24 questions, 17 had 80% or more answers, which means that this information should be part of the prescription model.

<p>The last two decades witnessed an increasing emphasis on reverse logistics (RL). Our thesis attempts to investigate two research problems in RL and explore game theoretic applications in this field.</p> <p>In Chapter 1, we introduce SCM, RL, relevant game theoretic applications, and the organizational structure of this thesis.</p> <p>In Chapter 2, we address a newsvendor problem with resalable returns. We develop a basic model with order quantity as the single decision variable and conduct concavity analysis. We also develop a general model in which the retailer determines both order quantity and two inter-period inventory thresholds. We use simulation to investigate the timing effect of both customer demands and returns on the retailer's decision making.</p> <p>In Chapter 3, we explore the application of game theoretic models with incomplete information in inventory management. Games with incomplete information may provide a more realistic modeling framework. We hope this exposition be helpful to researchers interested in applying game theoretic models and computing equilibriums in their specific problems in SCM and RL.</p> <p>In Chapter 4 we consider a remanufacturing competition problem between an original equipment manufacturer (OEM) and a pure remanufacturer (REM) with the OEM's incomplete information on the REM's unit cost. We apply the type-III model in Chapter 3 for formulation and derive the closed-form Bayesian Nash equilibrium. We use sensitivity analysis to investigate the effect of such incomplete information on both competitors' decision making.</p> <p>We summarize in Chapter 5 and provide a general direction for future research on game theoretic applications in RL.</p> / Doctor of Philosophy (PhD)

Coordination is a desirable feature in many multi-agent systems, such as robotic, social and economic networks, allowing the execution of tasks that would be impossible by individual agents. This thesis addresses two problems in stochastic coordination where each agent make decisions strategically, taking into account the decisions of its neighbors over a regular network. In the first problem, we study the coordination in a team of strategic agents choosing to undertake one of the multiple tasks. We adopt a stochastic framework where the agents decide between two distinct tasks whose difficulty is randomly distributed and partially observed. We show that a Nash equilibrium with a simple and intuitive linear structure exists for textit{diffuse} prior distributions on the task difficulties. Additionally, we show that the best response of any agent to an affine strategy profile can be nonlinear when the prior distribution is not diffuse. Then, we state an algorithm that allows us to efficiently compute a data-driven Nash equilibrium within the class of affine policies. In the second problem, we assume that the payoff structure of the coordination game corresponds to a single task allocation scenario whose difficulty is perfectly observed. Since there are multiple Nash equilibria in this game, the agents must use a distributed stochastic algorithm know as textit{log linear learning} to play it multiple times. First, we show that this networked coordination game is a potential game. Moreover, we establish that for regular networks, the convergence to a Nash equilibrium depends on the ratio between the task-difficulty parameter and the connectivity degree according to a threshold rule. We investigate via simulations the interplay between rationality and the degree of connectivity of the network. Our results show counter-intuitive behaviors such as the existence of regimes in which agents in a network with larger connectivity require less rational agents to converge to the Nash equilibrium with high probability. Simultaneously, we examined the characteristics of both regular graphical coordination games and non-regular graphical games using this particular bi-matrix game model. / Master of Science / This thesis focuses on addressing two problems in stochastic coordination among strategic agents in multi-agent systems, such as robotic, social, and economic networks. The first problem studies the coordination among agents when they need to choose between multiple tasks whose difficulties are randomly distributed and partially observed. The thesis shows the existence of a Nash equilibrium with a linear structure for certain prior distributions, and presents an algorithm to efficiently compute a data-driven Nash equilibrium within a specific class of policies. The second problem assumes a single task allocation scenario, whose difficulty is perfectly observed, and investigates the use of a distributed stochastic algorithm known as log-linear learning to converge to a Nash equilibrium. The thesis shows that the convergence to a Nash equilibrium depends on the task-difficulty parameter and the connectivity degree of the network, and explores the influence of rationality of the agents and the connectivity of the network on the learning process. Overall, the thesis provides insights into the challenges and opportunities in achieving coordination among strategic agents in multi-agent systems.

在政府提倡金融自由化、國際化的引導下，台灣金融管制解放，金融機構擺脫過去寡占經營的局面紛紛林立，為了因應市場競爭，各種金融產品不斷推陳出新，放款限制亦不斷寬鬆，造成市場一片蓬勃。然而從1997年金融危機的發生，導致企業跳票的個案中，使我們注意到企業在自由化時期藉籌措資金之便，大行金錢投機遊戲，以股票質押再行借款投資。此種高度的財務槓桿操作，一旦面臨危機衝擊，抵押品價值下滑，勢必發生連鎖反應而危及營運。 本研究從市場資訊不對稱觀點說明，公司抵押品價值（淨值）下滑，對借款者的債務保障價值減少，加速資訊不對稱之二大問題───道德危機和逆選擇，促使經濟雪上加霜，引發全面性危機。本研究的實證結果如下： 1.台灣自1990年代後，紛紛以股票質押借款，放款隨股價變動而有循環性調整，銀行抵押放款捲入股價波動，脆弱的金融體系一旦因應景氣情勢緊縮信用，對經濟產生進一步抵押品效果。 2.由此次台灣企業財務危機教訓可知，出問題的多為股票質押，不動產質押因應危機的反映較低且台灣不動產不景氣已多年，銀行資本已消化部分壞帳。實證結果亦顯示股票質押相對不動產更有助長經濟向下沉淪的力量。 3.各國經濟結構有別，對抵押品寄予不同程度擔保。所得低的國家，債信程度亦低，金融機構愈仰賴抵押品進行貸款評估，但其效果並不顯著，表示所得並不是唯一考量債信的因素之一。儲蓄對利率的敏感度也是各國因應危機受創不一的因素，當政府為了捍衛匯率，提高利率的結果,無可避免的重創經濟體系，而逃離的資金對利率敏感度低下，卻不易回流至金融體系，整體而言，勢必對一國景氣恢愎速度造成阻力。 4.放款對股價彈性大小變動的幅度和綜合危機判斷指數成負相關。代表愈仰賴抵押品作為貸款條件的國家在面臨危機發生時，會因抵押品效果使經濟更加惡化。

搜尋理論是訊息經濟學中很重要的一部份，搜尋行為有助於決策約滿意度。本文研究的重點主要在於商品市場上的消費者價格搜尋、消費決策及其與政府課稅之間的關係。 在消費者採用連續搜尋，而且假設搜尋不可回溯，搜尋次數有限，價格分配已知時，搜尋決策其有保留價格的性質。以「向後求解」的方法，消費者可以得到各期之保留價格。保留價格是稟賦所得、搜尋成本、其他財貨價格、效用函數及價格分配型態的函數。假設其他條件不變，若稟賦所得減少，搜尋成本增加，則保留價格上升；隨著已搜尋約次數增加，保留價格跟著上升，亦即消費者在搜尋過程中會愈來愈願意接受較高的價格。 消費者從事搜尋行為時的保留價格和搜尋成本會對消費決策產生影響。保留價格不但決定停止搜尋的時機，也會影饗真正從事購買的價格；可以用來消費的淨所得因搜尋次數的多寡而增減，所以等於也受到保留價格的影響。外生變數變動會改變保留價格，進而間接影饗預期需求，包括改變可接受價格之範圍和停止搜尋機率；然而，同時也會直接影響需求函數，總合上述兩者才能決定對預期需求的影響為何，結果通常使預期需求增減不易判別。預期搜尋次數與保留價格成反向關係。 政府對需要搜尋的財貨課從量稅，使價格分配向右平移，保留價格會隨之上升，但上升的幅度不會剛好等於稅率。稅率愈高，保留價格上升幅度愈大。平均而言，消費者因為租稅轉嫁必須支付較高的價格，所以會減少需求，此為課稅的直接影響；再加上提高保留價格而封預期需求產生間接影響，結果需求增減不易確定。在政府追求社會福利極大且受限於固定稅收之下，得到價格訊息不完全的最適租稅法則，比價格確定時多出了社會搜尋效果，包括課稅對願接受價格上下限和停止搜尋機率的影響，主要是透過課稅改變保留價格來達成。 假若效用函數為 Cobb-Douglas 的型態，價格呈一致分配，則由模擬方析結果發現，課稅後需搜尋財貨預期需求量減少，不需搜尋財貨預期需求量增加，預期效用降低且搜尋次數減少。

Στην παρούσα μεταπτυχιακή διπλωματική εργασία χρησιμοποιούμε έννοιες και εργαλεία της Θεωρίας Παιγνίων με σκοπό να μελετήσουμε την απόδοση μηχανισμών κατανομής διαιρέσιμων πόρων εστιάζοντας κυρίως στον μηχανισμό αναλογικής κατανομής. Σύμφωνα με αυτόν τον μηχανισμό, ένα σύνολο χρηστών ανταγωνίζονται για ένα διαιρέσιμο πόρο -- όπως το εύρος ζώνης ενός τηλεπικοινωνιακού καναλιού -- υποβάλλοντας προσφορές. Ο μηχανισμός κατανέμει σε κάθε χρήστη ένα μέρος του πόρου το οποίο είναι ανάλογο της προσφοράς του και συλλέγει ένα ποσό ίσο με την προσφορά αυτή ως πληρωμή. Οι χρήστες στοχεύουν στη μεγιστοποίηση της ωφέλειας τους και συμπεριφέρονται στρατηγικά αλλάζοντας τις προσφορές τους με σκοπό να το πετύχουν. Έτσι, ο μηχανισμός ορίζει ένα παιχνίδι αναλογικής κατανομής. Παρουσιάζουμε γνωστά αποτελέσματα από τη σχετική βιβλιογραφία καθώς και νέα βελτιωμένα φράγματα για το κόστος της αναρχίας ως προς το κοινωνικό όφελος για συσχετιζόμενες ισορροπίες στο μοντέλο πλήρους πληροφόρησης και για ισορροπίες κατά Bayes-Nash στο μοντέλο ελλιπούς πληροφόρησης. Πιο συγκεκριμένα, παρουσιάζουμε ένα κάτω φράγμα 1/2 για το κόστος της αναρχίας ως προς τις προαναφερθείσες έννοιες ισορροπίας, βελτιώνοντας σημαντικά το προηγούμενο καλύτερο κάτω φράγμα 26.8% που πρόσφατα απέδειξαν οι Syrgkanis και Tardos (STOC 2013). Επίσης, μελετάμε για πρώτη φορά τη περίπτωση όπου οι χρήστες διαθέτουν περιορισμένους προϋπολογισμούς και παρουσιάζουμε ένα κάτω φράγμα περίπου 36% και ένα άνω φράγμα 50% για το κόστος της αναρχίας χρησιμοποιώντας ως αντικειμενική συνάρτηση το αποτελεσματικό όφελος το οποίο λαμβάνει υπόψη προϋπολογισμούς. / In this thesis, we use notions and techniques from Game Theory in order to analyze the performance of divisible resource allocation mechanisms focusing mainly on the proportional allocation mechanism. According to this mechanism, a set of users are competing for a divisible resource -- such as bandwidth of a communication link -- by submitting bids. The mechanism allocates to each user a fraction of the resource that is proportional to the user's bid and collects an amount equal to the bid as payment. Users aim to maximize their individual utility and act strategically in order to achieve their goal. Hence, the mechanism defines a proportional allocation game. We cover previously known results from the related literature and present new bounds on the price of anarchy with respect to the social welfare over coarse-correlated and Bayes-Nash equilibria in the full and incomplete information settings, respectively. In particular, we prove a lower bound of $1/2$ for the price of anarchy over both equilibrium concepts, significantly improving the previously best known lower bound, presented by Syrgkanis and Tardos (STOC 2013). Furthermore, we study for the first time the scenario where users have budget constraints and present lower bounds on the price of anarchy using the effective welfare (which takes budgets into account) as an objective function.