Influencers in Multiplayer Online Shooters Evidence of Social Contagion in Playtime and Social Play

In a wide range of social networks, people’s behavior is influenced by social contagion: we do what our network does. Networks often feature particularly influential individuals, commonly called influencers. Existing work suggests that in-game social networks in online games are similar to real life social networks in many respects. However, we do not know whether there are in-game equivalents to influencers. We therefore applied standard social network features used to identify influencers to the online multiplayer shooter Tom Clancy’s The Division. Results show that network features defined influencers had indeed an outsized impact on playtime and social play of players joining their in-game network

On resource distribution in network coordination game

Product adoption is an important topic from the marketing perspective. People want to understand how a new product penetrates a market. Researchers propose many models to capture product adoption growth as well as the decision-making process for individuals. In this work, we identify the lack of consideration in current research of how much time people spend on their friends and families. We develop a new game-theoretical framework to model how people spend their time. Also, we analyze the extreme cases in this model. In addition, we do extensive simulations to understand the average case performance of the steady state. We find that our resource allocation model is a potential game and the efficiency of the steady state of the game is very good on average

Essays on the economics of social interactions

Defence date: 26 June 2019Examining Board: Prof. David K. Levine, European University Institute (Supervisor); Prof. Andrea Mattozzi, European University Institute; Prof. Yann Bramoullé, CNRS, Aix-Marseille School of Economics (External Co-Supervisor); Prof. Dino Gerardi, Collegio Carlo AlbertoThis dissertation consists of three self-contained essays on the economics of social interactions. The first chapter is coauthored with Lorenzo Verstraeten. Knowing that Individuals interact with their peers, we study how a social planner can intervene, changing these interactions, in order to achieve a particular objective. When the objective is welfare maximization, we describe the interventions for games of strategic complements and strategic substitutes. We show that, for strategic complements, the planner uses resources to target central players; while she divides individuals into separated communities in the case of strategic substitutes. We study which connections she targets in order to achieve these goals. The second chapter is coauthored with Lorenzo Verstraeten and analyzes a model of contagion on social network. We ask how a social planner should intervene to prevent contagion. We characterize the optimal intervention and the cost associated. We discuss the intuition behind the choice of the planner and we provide comparative static on the cost of intervention for different type of network. In the third chapter I develop a theoretical study about groups relationship and ask whether intragroup cooperation crowd-out intergroup cooperation. I consider a gift-giving game where cooperation endogenously arises, within and across groups. Cooperation is sustained through peer punishment with the help of a group specific monitoring technology. I specify under which conditions cooperation crowding-out occur. I identify two classes of equilibrium: a Sorting equilibrium where guilty players prefer to be matched outside their group due to a less efficient Out-Group monitoring technology, and a Non Sorting equilibrium where the higher level of In-Group cooperation makes it more attractive for everybody. I then compare their welfare properties and draw conclusions on optimal punishment levels.Chapter 1: Optimal intervention for network games 1 Introduction 2 Literature Review 3 The Model 3.1 The setup 3.2 Equilibrium 4 Closest network structure to implement a chosen vector of actions 4.1 Case 1: Unconstrained intervention 4.2 Case 2: Symmetric intervention 4.3 Case 3: Sparse intervention 5 Closest network structure that maximizes welfare 11 5.1 The planner's problem 5.2 Equilibrium pro_le's reaction to planner's intervention 6 Comparison with GGG 7 Network structure analysis 8 Other Interventions 9 Appendix 9.1 Proof of theorem 1 9.1.1 Projection of the equilibrium pro_le before intervention 9.1.2 Projection of the equilibrium pro_le after intervention 9.1.3 Comparing the ratio of projections on two di_erent right singular vectors 9.2 Proof of proposition 4 9.3 Optimal intervention under symmetry constraint Chapter 2: Stopping contagion: optimal network intervention 1 Introduction 2 Literature Review 3 3 The Model 3.1 Discussion of the epidemic threshold 4 Optimal immunization 5 Applications 5.1 Example 1 5.1.1 Initial structure 5.1.2 Post-intervention structure 5.1.3 Comparative statics of the cost of intervention 5.2 Example 2 5.2.1 Initial structure 5.2.2 Post-intervention structure 5.2.3 Comparative statics of the cost of intervention 5.3 Example 3: homogeneous versus heterogeneous networks 6 Conclusion Chapter 3: Does intragroup cooperation crowd-out intergroup cooperation? 1 Introduction 2 Literature Review 3 The Model 3.1 Stage Games 3.1.1 Pre-matching Stage: Choice of the Targets of the Signalling Technology 3.1.2 Matching Process 3.1.3 Post-matching Stage: Gift-Giving Stage 3.2 Signal Processing 3.3 Strategies and Equilibrium de_nition 3.3.1 Strategies 3.3.2 Equilibrium De_nition 4 Players Incentives 4.1 Old Players Incentives 4.1.1 Optimal Choice when xi = _(gi; gj ; sj) 4.1.2 Optimal Choice when xi 6= _(gi; gj ; sj) 4.2 Young Players Incentives 4.2.1 Non-Sorting Equilibrium 4.2.2 Sorting Equilibrium 5 Typology of equilibrium 68 6 Non Sorting Equilibrium and Crowding-out 69 6.1 Case 4: _0; _1 < 1 and ICNS _0 ; ICNS _1 are binding 6.2 Case 5: _0 < 1; _1 = 1, ICNS _0 is binding and ICNS _1 is not binding 6.3 Case 6: _0 = 1; _1 = 1, no Incentive Constraint is binding 7 Sorting versus Non Sorting Equilibria 7.1 Drivers of Equilibrium type 7.2 Welfare analysis 8 Conclusio

Contagion Risk and Network Design

Individuals derive bene ts from their connections, but these may, at the same time, transmit external threats. Individuals therefore invest in security to protect themselves. However, the incentives to invest in security depend on their network exposures. We study the problem of designing a network that provides the right individual incentives. Motivated by cybersecurity, we rst study the situation where the threat to the network comes from an intelligent adversary. We show that, by choosing the right topology, the designer can bound the welfare costs of decentralized protection. Both over-investment as well as under-investment can occur depending on the costs of security. At low costs, over-protection is important: this is addressed by discon- necting the network into two unequal components and sacri cing some nodes. At high costs, under-protection becomes salient: it is addressed by disconnecting the network into equal components. Motivated by epidemiology, we then turn to the study of random attacks. The over-protection problem is no longer present, whereas under-protection problems is mitigated in a diametrically opposite way: namely, by creating dense networks that expose the individuals to the risk of contagion

Knowing the unknowns: financial policymaking in uncertainty

How do policymakers make decisions during financial market uncertainty? I develop a straightforward framework of policymaking in uncertainty. To overcome uncertainty, policymakers gather information using strategies discussed across a variety of political science disciplines. Policymakers need information to be able to make goal-oriented decisions. The information strategies actors choose are conditioned on the uncertainty problems they face. In turn, the information they receive impacts their policy decisions. My three empirical papers investigate what strategies are likely to be chosen in different types of uncertainty and how these choices affect policy decisions. My first paper, co-written with Mícheál O’Keeffe, develops a signaling game that policymakers play when they perceive data uncertainty, i.e. uncertainty about economic fundamentals. The model is supported empirically with analytic narratives of recent crises in Korea and Ireland. My following two papers deal with situations of increasing causal uncertainty, i.e. uncertainty about how actions cause outcomes. In both of these papers I use Multi-state Event History Analysis. I find that when there is high causal uncertainty policymakers tend to use learning strategies that start with international-level policy recommendations. These recommendations are then updated with the experiences of regional peers who have adopted them. Beyond creating and finding evidence for a parsimonious framework of decisionmaking in uncertainty, I make a number of other contributions to political economy. I extend the empirical tools researchers can use to understand decisions in complex choice environments. I provide evidence that making financial bureaucrats “independent" does not ensure positive outcomes. Specifically, it does not guarantee that financial bureaucrats will provide accurate information needed for effective policymaking

Lock-in through passive connections

We consider a model of social coordination and network formation where agents decide on an action in a coordination game and on whom to establish costly links to. We study the role of passive connections; these are connections to a given agent that are supported by other agents. Such passive connections may inhibit agents from switching actions and links, as this may result in a loss of payoff received through them. When agents are constrained in the number of links they may support, this endogenously arising form of lock-in leads to mixed profiles, where different agents choose different actions, being included in the set of Nash equilibria. Depending on the precise parameters of the model, risk- dominant, payoff- dominant, or mixed profiles are stochastically stable. Thus, agents’ welfare may be lower as compared to the case where payoff is only received through active links. The network formed by agents plays a crucial role for the propagation of actions, it allows for a contagious spread of risk dominant actions and evolves as agents change their links and actions

Reflections on the future business model of European banks and the supervisory approach

Relevant forces are reshaping the banking sector and redefining banks’ business models. On the one hand, banks have been facing structural difficulties, such as a prolonged low interest rate environment and the costs of excess capacity. In addition, banks need to deal with more recently developing challenges, like the digital transformation, the entrance of new competitors in the banking sector and the climate change. A demanding regulatory environment and the impact of the COVID-19 pandemic further aggravate the situation. As a result, European banks are not being able to produce enough returns to cover their cost of capital, making it necessary to urgently face these challenges. To that purpose, banks may adopt different strategies, some of them complementary, among which the following can be highlighted: the reduction of overcapacity, consolidation, diversification or specialisation and the exploitation of the value of long-term relations with clients, as well as taking advantage of the opportunities stemming from digitalization and sustainable finance. Supervisors will need to stay abreast of the changes in the banking environment and closely monitor the adaptation processes. This article is intended to serve as a basis for discussion, given that several of the issues raised are controversial and uncertain under the current fast changing environment

Reflections on the future business model of European banks and the supervisory approach

Importantes factores están reconfigurando el sector bancario y redefiniendo los modelos de negocio de las entidades. Las entidades han venido afrontando dificultades estructurales, como un entorno de bajos tipos de interés prolongado o el exceso de capacidad instalada. A esto se añaden otros retos más recientes, como la transformación digital, los nuevos competidores en el mercado bancario y el cambio climático. Adicionalmente, un entorno regulatorio exigente y el impacto del COVID-19 suponen una presión añadida. Como resultado, los bancos europeos no están siendo capaces de producir resultados que cubran el coste del capital, lo que hace necesario afrontar con urgencia estos retos. Para ello, existen distintas estrategias posibles, algunas de ellas complementarias, entre las que se pueden destacar: la reducción de la capacidad instalada, la consolidación bancaria, la diversificación o especialización y la explotación del valor de la banca relacional, así como el aprovechamiento de las oportunidades derivadas de la digitalización y las finanzas sostenibles. El supervisor deberá estar al nivel de los cambios que se produzcan en el entorno bancario y seguir de cerca los procesos de adaptación. El propósito de este artículo es servir de base para el debate, dada la controversia existente y la incertidumbre que rodea a algunas de estas cuestiones en un entorno como el actual, que cambia con rapidez