The price of re-establishing perfect, almost perfect or public monitoring in games with arbitrary monitoring

This paper establishes a connection between the notion of observation (or monitoring) structure in game theory and the one of communication channels in Shannon theory. One of the objectives is to know under which conditions an arbitrary monitoring structure can be transformed into a more pertinent monitoring structure. To this end, a mediator is added to the game. The objective of the mediator is to choose a signalling scheme that allows the players to have perfect, almost perfect or public monitoring and all of this, at a minimum cost in terms of signalling. Graph coloring, source coding, and channel coding are exploited to deal with these issues. A wireless power control game is used to illustrate these notions but the applicability of the provided results and, more importantly, the framework of transforming monitoring structures go much beyond this example.Comment: Proc. of the 4th ACM International Workshop on Game Theory in Communication Networks, 201

Transforming Monitoring Structures with Resilient Encoders. Application to Repeated Games

An important feature of a dynamic game is its monitoring structure namely, what the players effectively see from the played actions. We consider games with arbitrary monitoring structures. One of the purposes of this paper is to know to what extent an encoder, who perfectly observes the played actions and sends a complementary public signal to the players, can establish perfect monitoring for all the players. To reach this goal, the main technical problem to be solved at the encoder is to design a source encoder which compresses the action profile in the most concise manner possible. A special feature of this encoder is that the multi-dimensional signal (namely, the action profiles) to be encoded is assumed to comprise a component whose probability distribution is not known to the encoder and the decoder has a side information (the private signals received by the players when the encoder is off). This new framework appears to be both of game-theoretical and information-theoretical interest. In particular, it is useful for designing certain types of encoders that are resilient to single deviations and provide an equilibrium utility region in the proposed setting; it provides a new type of constraints to compress an information source (i.e., a random variable). Regarding the first aspect, we apply the derived result to the repeated prisoner's dilemma.Comment: Springer, Dynamic Games and Applications, 201

A partial folk theorem for games with private learning

The payoff matrix of a finite stage game is realized randomly, and then the stage game is repeated infinitely. The distribution over states of the world (a state corresponds to a payoff matrix) is commonly known, but players do not observe nature’s choice. Over time, they can learn the state in two ways. After each round, each player observes his own realized payoff (which may be stochastic, conditional on the state), and he observes a noisy public signal of the state (whose informativeness may vary with the actions chosen). Actions are perfectly observable. The result is that for any function that maps each state to a payoff vector that is feasible and individually rational in that state, there is a sequential equilibrium in which patient players learn the realized state with arbitrary precision and achieve a payoff close to the one specified for that state. That result extends to the case where there is no public signal, but instead players receive very closely correlated private signals of the vector of realized payoffs.Repeated games, learning, folk theorem

Enforcing International Law: Implications for an Effective Global Warming Regime

Syftet med denna studie var att undersöka den antibakteriella effekten hos ett polyestertyg med tunna invävda koppartrådar. Frågeställningen som skulle besvaras var ifall koppartyget hade en baktericid eller bakteristatisk effekt. Koppartyget är ännu i prototypstadie och om det visar sig ha antibakteriella egenskaper är det tänkt att användas inom klinisk verksamhet för att förhindra bakterietillväxt i sår och andra känsliga lokaler. Koppar är ett essentiellt spårämne, men har också antimikrobiella egenskaper som utövas genom ett brett spektra av mekanismer där skador på cellmembranet är en av de viktigare. Metoderna som användes för att inokulera bakterier på tyget var absorptionsmetoden, där en näringsbuljong innehållande Staphylococcus aureus ATCC 6538 pipetterades på tygproverna, och transfermetoden där tygproverna trycktes mot en agar som racklats med peptonsaltlösning innehållande S. aureus. Totalantalet viabla bakterier per tygprov beräknades efter kort kontakt (<1min) och inkubering (18-24 h vid 37±2°C) genom att räkna viable count. Resultaten efter inkubering visade signifikant skillnad i totalantal bakterier mellan koppartyget och negativ kontroll i tre av fyra försök. Kort kontakt visade tendens till viss antibakteriell effekt. Slutsatsen är att koppartyget skadade och dödade bakterier då de fick inkubera på tyget, medan fler försök behövs för att säkerställa effekten av kort kontakt med koppartyget. The purpose of this study was to test the antibacterial effect of thin copper treads woven into a polyester fabric. The investigation was done by inoculation of Staphylococcus aureus strain ATCC 6538 to the fabric and evaluation of the number of viable cells post exposure by viable count. The issue to be answered was whether the copper fabric had a bactericide or bacteriostatic effect? The fabric is still in prototype stage, and if proven to have antibacterial properties the aim is to use it to prevent bacterial growth in wounds and other vulnerable locations in clinical care. Copper is an essential trace element, but also has antimicrobial properties through a wide range of mechanisms where cell membrane damage is one of the more important. Methods used for inoculation was the absorption method, where a nutrient broth containing S. aureus was pipetted on to the fabric specimens, and the transfer method where the fabric specimens were pressed onto an agar plate that had previously been spread with peptone salt solution containing S. aureus. Total number of bacteria per fabric specimen after short contact (<1 min) and incubation (18-24 h at 37±2°C) was calculated. Incubation showed significant difference in total number of bacteria between the copper fabric and negative control in three of four tests. Short contact showed a tendency of antibacterial effect. The conclusion was that the copper fabric harmed and killed bacteria during incubation but that more records would be needed to be sure about the effects of short contact on bacteria

Non-Governmental Public Norm Enforcement in Large Societies as a Two-Stage Game of Voluntary Public Good Provision.

In small groups, norm enforcement is achieved through mutual punishment and reward. In large societies, norms are enforced by specialists such as government officials. However, not every public cause is overseen by states, for instance those organized at the international level. This paper shows how non-governmental norm enforcement can emerge as a decentralized equilibrium. As a first stage, individuals voluntarily contribute to a non-governmental agency that produces an incentive system. The second stage is the provision of a public good on the basis of private contributions. The incentive system punishes and rewards deviations from the norm for contributions by means of public approval or disapproval of behavior. It is shown that, even in large populations, nongovernmental norm enforcement can be supported in a non-cooperative equilibrium of utility-maximizing individuals.

Protocol Invariance and the Timing of Decisions in Dynamic Games

We characterize a class of dynamic stochastic games that we call separable dynamic games with noisy transitions and establish that these widely used models are protocol invariant provided that periods are sufficiently short. Protocol invariance means that the set of Markov perfect equilibria is nearly the same irrespective of the order in which players are assumed to move within a period. Protocol invariance can facilitate applied work and renders the implications and predictions of a model more robust. Our class of dynamic stochastic games includes investment games, R&D races, models of industry dynamics, dynamic public construction games, asynchronously repeated games, and many other models from the extant literature

Should we pay for ecosystem service outputs, inputs or both?

Payments for ecosystem service outputs have recently become a popular policy prescription for a range of agri-environmental schemes. The focus of this paper is on the choice of contract instruments to incentivise the provision of ecosystem service outputs from farms. The farmer is better informed than the regulator in terms of hidden information about costs and hidden-actions relating to effort. The results show that with perfect information, the regulator can contract equivalently on inputs or outputs. With hidden information, input-based contracts are more cost effective at reducing the informational rent related to adverse selection than output-based contracts. Mixed contracts are also cost-effective, especially where one input is not observable. Such contracts allow the regulator to target variables that are “costly-to-fake” as opposed to those prone to moral hazard such as effort. Further results are given for fixed price contracts and input-based contracts with moral hazard. The model is extended to include a discussion of repeated contracting and the scope that exists for the regulator to benefit from information revealed by the initial choice of contract. The models are applied to a case study of contracting with farmers to protect high biodiversity native vegetation that also provides socially-valuable ecosystem services

Antidumping: Welfare Enhancing Retaliation?

Over the last two decades, the use of antidumping (AD) measures has been characterized by two main features. First and foremost, it has increased dramatically. Additionally, it has not - to a large extent - been used to counteract the existence of dumping, but rather in a strategic or retaliatory fashion. These empirical findings have led many to propose the elimination of this instrument altogether, on the basis that its current use is arbitrary and, consequently, welfare reducing. We argue that these concerns may be unfounded since, in a world of restricted trade policy instruments, a retaliatory use of AD might be welfar enhancing. By modeling the trade relationship between countries as a repeated game of hidden information, we show that retaliation can be welfare increasing with respect to a rigid rule on the use of AD. We stress the fact that, underlying this result, is the unavailability of transfers or export subsidies in the current world trading system.