<p>We study the application of reputation as an instigator of beneficial user behavior in selfish routing and when the network users rely on the network coordinator for information about the network. Instead of using tolls or artificial delays, the network coordinator takes advantage of the users' insufficient data, in order to manipulate them through the information he provides. The issue that arises then is what can be the coordinator's gain without compromising by too much on the trust the users put on the information provided, i.e., by maintaining a reputation for (at least some) trustworthiness.</p> <p>Our main contribution is the modeling of such a system as a repeated game of incomplete information in the case of single-commodity general networks. This allows us to apply known folk-like theorems to get bounds on the price of anarchy that are better than the well-known bounds without information manipulation.</p> / Master of Computer Science (MCS)

This dissertation consists of three essays that adopt both theoretical and empirical methods of analysis to study certain economies in which the incomplete information and the strategic complementarities between players are important. Chapter 1 explains the topics discussed in the subsequent chapters and gives a brief survey on the literature. In Chapter 2, I revise a traditional global game model by dividing the continuum of players into a group of speculators and a group of stakeholders. It is found that the uniqueness property remains in the new game. Then I extend the static game to a two-stage game and investigate the efficacies of certain label changing mechanisms proposed by the authority to stabilize the regime in the dynamic context. It is shown that a label changing mechanism allowing for downward social mobility may not work, whereas a label changing mechanism allowing for upward social mobility generally makes the regime more stable. In Chapter 3, I add a speculator and an authority to a bank-run model to investigate how the speculator endangers a business or an economy, and what the authority can do about it. In particular, I show that the speculator can increase the financial system's vulnerability by serving as a coordinating device for the investors and thus triggering the crisis. It is further shown that deterring the speculator may not undo the speculator's impact because of multiplicity problem; rewarding holding investors is useless; and eliminating the preemption motives among investors works given enough effort. A discussion of the 1997 Asian financial crisis and the IMF's role in it is also included. Chapter 4 develops a repeated beauty-contest game to investigate the effect of previous winners' actions on the spread of subsequent players' actions. I first characterize the unique equilibrium of the game. Then I focus on the equilibrium dynamics of several variances depicting different forms of action variability. It is found that whether or not a specific variance diminishes over time depends on the relative precision of public and private signals. To illustrate the theoretical results, I conduct an empirical study on the Miss Korea contest. It is found that the contestants' faces have been converging to the ``true beauty'' overall, but diverging from each other over the last 20 years. Chapter 5 concludes. / Ph. D.

This doctoral thesis consists of five research articles on the general topic of optimal decision making under uncertainty in a Bayesian framework. The papers are preceded by three introductory chapters. Papers I and II are dedicated to the problem of finding an optimal stopping strategy to liquidate an asset with unknown drift. In Paper I, the price is modelled by the classical Black-Scholes model with unknown drift. The first passage time of the posterior mean below a monotone boundary is shown to be optimal. The boundary is characterised as the unique solution to a nonlinear integral equation. Paper II solves the same optimal liquidation problem, but in a more general model with stochastic regime-switching volatility. An optimal liquidation strategy and various structural properties of the problem are determined. In Paper III, the problem of sequentially testing the sign of the drift of an arithmetic Brownian motion with the 0-1 loss function and a constant cost of observation per unit of time is studied from a Bayesian perspective. Optimal decision strategies for arbitrary prior distributions are determined and investigated. The strategies consist of two monotone stopping boundaries, which we characterise in terms of integral equations. In Paper IV, the problem of stopping a Brownian bridge with an unknown pinning point to maximise the expected value at the stopping time is studied. Besides a few general properties established, structural properties of an optimal strategy are shown to be sensitive to the prior. A general condition for a one-sided optimal stopping region is provided. Paper V deals with the problem of detecting a drift change of a Brownian motion under various extensions of the classical Wiener disorder problem. Monotonicity properties of the solution with respect to various model parameters are studied. Also, effects of a possible misspecification of the underlying model are explored.

Container Line Supply Chain (CLSC), which transports cargo in containers and accounts for approximately 95 percent of world trade, is a dominant way for world cargo transportation due to its high efficiency. However, the operation of a typical CLSC, which may involve as many as 25 different organizations spreading all over the world, is very complex, and at the same time, it is estimated that only 2 percent of imported containers are physically inspected in most countries. The complexity together with insufficient prevention measures makes CLSC vulnerable to many threats, such as cargo theft, smuggling, stowaway, terrorist activity, piracy, etc. Furthermore, as disruptions caused by a security incident in a certain point along a CLSC may also cause disruptions to other organizations involved in the same CLSC, the consequences of security incidents to a CLSC may be severe. Therefore, security analysis becomes essential to ensure smooth operation of CLSC, and more generally, to ensure smooth development of world economy. The literature review shows that research on CLSC security only began recently, especially after the terrorist attack on September 11th, 2001, and most of the research either focuses on developing policies, standards, regulations, etc. to improve CLSC security from a general view or focuses on discussing specific security issues in CLSC in a descriptive and subjective way. There is a lack of research on analytical security analysis to provide specific, feasible and practical assistance for people in governments, organizations and industries to improve CLSC security. Facing the situation mentioned above, this thesis intends to develop a set of analytical models for security analysis in CLSC to provide practical assistance to people in maintaining and improving CLSC security. In addition, through the development of the models, the thesis also intends to provide some methodologies for general risk/security analysis problems under complex and uncertain environment, and for some general complex decision problems under uncertainty. Specifically, the research conducted in the thesis is mainly aimed to answer the following two questions: how to assess security level of a CLSC in an analytical and rational way, and according to the security assessment result, how to develop balanced countermeasures to improve security level of a CLSC under the constraints of limited resources. For security assessment, factors influencing CLSC security as a whole are identified first and then organized into a general hierarchical model according to the relations among the factors. The general model is then refined for security assessment of a port storage area along a CLSC against cargo theft. Further, according to the characteristics of CLSC security analysis, the belief Rule base Inference Methodology using the Evidential Reasoning approach (RIMER) is selected as the tool to assess CLSC security due to its capabilities in accommodating and handling different forms of information with different kinds of uncertainty involved in both the measurement of factors identified and the measurement of relations among the factors. To build a basis of the application of RIMER, a new process is introduced to generate belief degrees in Belief Rule Bases (BRBs), with the aim of reducing bias and inconsistency in the process of the generation. Based on the results of CLSC security assessment, a novel resource allocation model for security improvement is also proposed within the framework of RIMER to optimally improve CLSC security under the constraints of available resources. In addition, it is reflected from the security assessment process that RIMER has its limitations in dealing with different information aggregation patterns identified in the proposed security assessment model, and in dealing with different kinds of incompleteness in CLSC security assessment. Correspondently, under the framework of RIMER, novel methods are proposed to accommodate and handle different information aggregation patterns, as well as different kinds of incompleteness. To validate the models proposed in the thesis, several case studies are conducted using data collected from different ports in both the UK and China. From a methodological point of view, the ideas, process and models proposed in the thesis regarding BRB generation, optimal resource allocation based on security assessment results, information aggregation pattern identification and handling, incomplete information handling can be applied not only for CLSC security analysis, but also for dealing with other risk and security analysis problems and more generally, some complex decision problems. From a practical point of view, the models proposed in the thesis can help people in governments, organizations, and industries related to CLSC develop best practices to ensure secure operation, assess security levels of organizations involved in a CLSC and security level of the whole CLSC, and allocate limited resources to improve security of organizations in CLSC. The potential beneficiaries of the research may include: governmental organizations, international/regional organizations, industrial organizations, classification societies, consulting companies, companies involved in a CLSC, companies with cargo to be shipped, individual researchers in relevant areas etc.

Cette thèse concerne les jeux différentiels à somme nulle et à deux joueurs avec information incomplète. La structure de l'information est liée à un signal que reçoivent les joueurs. Cette information est dite symétrique quand la connaissance du signal est la même pour les deux joueurs (le signal est public), et asymétrique quand les signaux reçus par les joueurs peuvent être différents (le signal est privé).Ces signaux sont révélés au cours du jeu. Dans plusieurs situations de tels jeux, il est montré dans cette thèse, l'existence d'une valeur du jeu et sa caractérisation comme unique solution d'une équation aux dérivées partielles.Un type de structure d'information concerne le cas symétrique où le signal est réduit à la connaissance par les joueurs de l'état du système au moment où celui-ci atteint une cible donnée (les données initiales inconnues sont alors révélées). Pour ce type du jeu, nous avons introduit des stratégies non anticipatives qui dépendent du signal et nous avons obtenu l'existence d'une valeur.Comme les fonctions valeurs sont en général irrégulières (seulement continues), un des points clefs de notre approche est de prouver des résultats d'unicité et des principes de comparaison pour des solutions de viscosité lipschitziennes de nouveaux types d'équation d'Hamilton-Jacobi-Isaacs associées aux jeux étudiés. / In this thesis we investigate two-person zero-sum differential games with incomplete information. The information structure is related to a signal communicated to the players during the game.In such games, the information is symmetric if both players receive the same signal (namely it is a public signal). Otherwise, if the players could receive different signals (i.e. they receive private signals), the information is asymmetric. We prove in this thesis the existence of value and the characterization of the value function by a partial differential equation for various types of such games.A particular type of such information structure is the symmetric case in which the players receive as their signal the current state of the dynamical system at the moment when the state of the dynamic hits a fixed target set (the unknown initial data are then revealed to both players). For this type of games, we introduce the notion of signal-depending non-anticipative strategies with delay and we prove the existence of value with such strategies.As the value functions are in general irregular (at most continuous), a crucial step of our approach is to prove the uniqueness results and the comparison principles for viscosity solutions of new types of Hamilton-Jacobi-Isaacs equation associated to the games studied in this thesis.

Cette thèse s'articule autour de deux grands thèmes: l'amélioration de la gestion des risques assurantiels souscrits par les entreprises d'assurance et l'intégration des techniques actuarielles et financières. L'intérêt majeur de notre démarche est de proposer de nouvelles méthodes modernes de gestion des risques pour les sociétés d'assurance, fournissant des alternatives pertinentes aux approches classiques des actuaires. Dans bon nombre de problèmes actuariels, l'information dont on dispose à propos des risques en présence n'est que partielle et il peut être intéressant d'obtenir des approximations de quantités d'intérêt (fonctions de répartition, primes stop-loss, coefficients d'ajustement, probabilités de ruine, etc.) basées sur les premiers moments des risques en présence. Dans tous les cas, il est évidemment très important de pouvoir évaluer la qualité de ces approximations. A cet égard, l'obtention de bornes sur ces quantités d'intérêt permet de contrôler l'erreur qui pourrait entacher l'approximation. Dans une telle perspective, la majeure partie de la thèse a pour cadre de travail les classes de risques partageant les mêmes premiers moments (notamment, moyenne, variance et coefficient de dissymétrie). L'existence de risques extrémaux par rapport à certaines relations d'ordres stochastiques de type convexe permet alors d'obtenir des bornes sur les quantités d'intérêt considérées. Dans certains cas, et ce afin d'obtenir des bornes plus précises, il peut également s'avérer intéressant de se restreindre à d'autres classes de risques. Par exemple, la classe des risques discrets, qui constitue un cas particulier de première importance en sciences actuarielles, a retenu toute notre attention. Cette thèse est composée d'articles (rédigés en anglais) publiés dans des revues nationales et internationales.

Chapter 2 considers technology adoption under both technological and subsidy uncertainties. Uncertainty in subsidies for green technologies is considered as an example. Technological progress is exogenous and modeled as a jump process with a drift. The analytical solution is presented for cases when there is no subsidy uncertainty and when the subsidy changes once. The case when the subsidy follows a time invariant Markov process is analyzed numerically. The results show that improving the innovation process raises the investment thresholds. When technological jumps are small or rare, this improvement reduces the expected time before technology adoption. However, when technological jumps are large or abundant, this improvement may raise this expected time. Chapter 3 studies technology adoption in a duopoly where the unbiased technological change improves production efficiency. Technological progress is exogenous and modeled as a jump process with a drift. There is always a Markov perfect equilibrium in which the firm with more efficient technology never preempts its rival. Also, a class of equilibria may exist that lead to a smaller industry surplus. In these equilibria either of the firms may preempt its rival in a set of technology efficiency values. The first investment does not necessarily happen at the boundary of this set due to the discrete nature of the technology progress. The set shrinks and eventually disappears when the difference between firms’ efficiencies increases. Chapter 4 studies the behavior of two firms after a new investment opportunity arises. Firms either invest immediately or wait until market uncertainty is resolved. Two types of separating equilibrium are possible when sunk costs are private information. In the first type the firm with lower cost invests first. In the second type the firm with higher cost invests first leading to a smaller industry surplus. The results indicate that the second type is possible only for strictly negatively correlated sunk costs. Numerical analysis illustrates that when first mover advantage is large, the firm that delays the investment should be almost certain about its rival’s sunk cost. When market risk increases, the equilibria can exist when the firm is less certain. / text

abstract: One theoretical research topic in organizational economics is the information issues raised in different organizations. This has been extensively studied in last three decades. One common feature of these research is focusing on the asymmetric information among different agents within one organization. However, in reality, we usually face the following situation. A group of people within an organization are completely transparent to each other; however, their characters are not known by other organization members who are outside this group. In my dissertation, I try to study how this information sharing would affect the outcome of different organizations. I focus on two organizations: corporate board and political parties. I find that this information sharing may be detrimental for (some of) the members who shared information. This conclusion stands in contrast to the conventional wisdom in both corporate finance and political party literature. / Dissertation/Thesis / Ph.D. Economics 2014

Questa tesi si compone di due capitoli indipendenti, ciascuno dei quali analizza il ruolo giocato dall’informazione pubblica endogenamente determinata in situazioni caratterizzate da decision-making decentralizzato e da complementarietà strategica. Il primo capitolo analizza un regime-change game, in cui un governo autoritario può influenzare il consenso popolare attraverso l’implementazione di uno strumento di policy. A policy implementata, i cittadini possono tentare di destituire il governo in carica attraverso una rivolta popolare, la cui probabilità di successo è proporzionale al numero di partecipanti, quest’ultimo proporzionale al livello medio di malcontento. Per migliorare l’efficacia del policy-making, il governo necessita di informazioni affidabili sul consenso popolare, tipicamente difficili da reperire. Tali informazioni sono potenzialmente destabilizzanti, poiché aiutano i cittadini a coordinare meglio la loro azione collettiva. I risultati suggeriscono che maggiore trasparenza è desiderabile ex ante per quei regimi che, in equilibrio, hanno maggiore probabilità di implementare delle politiche di consensus-building. Maggiori livelli di libertà di informazione dovrebbero quindi essere osservati in regimi né troppo deboli, né troppo forti. Il secondo capitolo propone un modello di bank run, in cui la presenza di un mercato secondario efficiente dal punto di vista informativo destabilizza una istituzione a priori solida, tramutando uno shock temporaneo di liquidità in una spirale di fire-sales. Gli investitori di un fondo open-ended posso richiedere la liquidazione anticipata delle proprie quote dopo aver ricevuto informazioni private riguardo alla qualità degli asset in portafogli. Per rimborsare le quote, il fund manager vende una quota di asset sul mercato secondario. I potenziali acquirenti estraggono informazione dall’osservazione dell’offerta aggregata: maggiori volumi d’offerta corrispondono ad un maggior numero di investitori pessimisti, e suggeriscono quindi che gli asset potrebbero essere di scarsa qualità. Temendo una spirale discendente dei prezzi, anche gli investitori meno pessimisti sono indotti, ex ante, a liquidare le proprie quote, ulteriormente sostenendo il feedback negativo. Quando l’informazione privata è sufficientemente imprecisa, complementarietà strategica nelle azioni degli investitori del fondo emerge endogenamente. / This dissertation consists of two essays, aimed at providing a sound theoretical investigation of the signaling role of (observed) collective behavior in environments characterized by incomplete information and strategic complementarity. The effects of both endogenous signaling and (the disclosure of) exogenous public information on the degree of coordination failure that arises from decentralized decision-making are analyzed in-depth. In the first chapter I analyze a regime-change game, where an authoritarian government can influence popular support via the implementation of costly policies. Citizens can challenge the government via a riot, whose chances to succeed increase with the unknown average popular discontent. In order to fine-tune its policy-making, the regime needs reliable information about popular consensus. Such information, however, improves the ability of citizens to coordinate their revolt. I show that public information is ex ante beneficial for those regimes which are more likely to build consensus via policy-making in equilibrium. Higher levels of media freedom should therefore be observed in regimes that are neither too weak, nor too strong. In the second chapter I study a bank run model, where the informational efficiency of a (secondary) financial market pushes into insolvency an a priori solvent institution after a temporary, non-fundamental liquidity shock. The most pessimistic investors of an open-ended fund are allowed to ask for the early liquidation of their share after receiving private information about the economic fundamentals of the fund’s portfolio of assets. Some of the assets in portfolio are sold in the secondary market to meet those investors’ requests. Higher volumes of early redemptions decrease both the current price, via a standard law-of-demand effect, and the future price, by signaling bad news to the market. Anticipating such effect, less pessimistic investors, too, opt for early liquidation, thus further exacerbating the price spiral. Strategic complementarity arises endogenously when investors’ private information is sufficiently poor. In this case, a spiral of fire sales is observed in equilibrium.

Cette thèse traite de l’établissement d’une plateforme logicielle nommée DaWeS permettant le déploiement et la gestion en ligne d’entrepôts de données alimentés par des données provenant de services web et personnalisés à destination des petites et moyennes entreprises. Ce travail s’articule autour du développement et de l’expérimentation de DaWeS. L’idée principale implémentée dans DaWeS est l’utilisation d’une approche virtuelle d’intégration de données (la médiation) en tant queprocessus ETL (extraction, transformation et chargement des données) pour les entrepôts de données gérés par DaWeS. A cette fin, un algorithme classique de réécriture de requêtes (l’algorithme inverse-rules) a été adapté et testé. Une étude théorique sur la sémantique des requêtes conjonctives et datalog exprimées avec des relations munies de limitations d’accès (correspondant aux services web) a été menée. Cette dernière permet l’obtention de bornes supérieures sur les nombres d’appels aux services web requis dans l’évaluation de telles requêtes. Des expérimentations ont été menées sur des services web réels dans trois domaines : le marketing en ligne, la gestion de projets et les services d’aide aux utilisateurs. Une première série de tests aléatoires a été effectuée pour tester le passage à l’échelle. / The role of data warehouse for business analytics cannot be undermined for any enterprise, irrespective of its size. But the growing dependence on web services has resulted in a situation where the enterprise data is managed by multiple autonomous and heterogeneous service providers. We present our approach and its associated prototype DaWeS [Samuel, 2014; Samuel and Rey, 2014; Samuel et al., 2014], a DAta warehouse fed with data coming from WEb Services to extract, transform and store enterprise data from web services and to build performance indicators from them (stored enterprise data) hiding from the end users the heterogeneity of the numerous underlying web services. Its ETL process is grounded on a mediation approach usually used in data integration. This enables DaWeS (i) to be fully configurable in a declarative manner only (XML, XSLT, SQL, datalog) and (ii) to make part of the warehouse schema dynamic so it can be easily updated. (i) and (ii) allow DaWeS managers to shift from development to administration when they want to connect to new web services or to update the APIs (Application programming interfaces) of already connected ones. The aim is to make DaWeS scalable and adaptable to smoothly face the ever-changing and growing web services offer. We point out the fact that this also enables DaWeS to be used with the vast majority of actual web service interfaces defined with basic technologies only (HTTP, REST, XML and JSON) and not with more advanced standards (WSDL, WADL, hRESTS or SAWSDL) since these more advanced standards are not widely used yet to describe real web services. In terms of applications, the aim is to allow a DaWeS administrator to provide to small and medium companies a service to store and query their business data coming from their usage of third-party services, without having to manage their own warehouse. In particular, DaWeS enables the easy design (as SQL Queries) of personalized performance indicators. We present in detail this mediation approach for ETL and the architecture of DaWeS. Besides its industrial purpose, working on building DaWeS brought forth further scientific challenges like the need for optimizing the number of web service API operation calls or handling incomplete information. We propose a bound on the number of calls to web services. This bound is a tool to compare future optimization techniques. We also present a heuristics to handle incomplete information.