Differential information in large games with strategic complementarities

We study equilibrium in large games of strategic complementarities (GSC) with differential information. We define an appropriate notion of distributional Bayesian Nash equilibrium and prove its existence. Furthermore, we characterize order-theoretic properties of the equilibrium set, provide monotone comparative statics for ordered perturbations of the space of games, and provide explicit algorithms for computing extremal equilibria. We complement the paper with new results on the existence of Bayesian Nash equilibrium in the sense of Balder and Rustichini (J Econ Theory 62(2):385–393, 1994) or Kim and Yannelis (J Econ Theory 77(2):330–353, 1997) for large GSC and provide an analogous characterization of the equilibrium set as in the case of distributional Bayesian Nash equilibrium. Finally, we apply our results to riot games, beauty contests, and common value auctions. In all cases, standard existence and comparative statics tools in the theory of supermodular games for finite numbers of agents do not apply in general, and new constructions are required

Rozwiązania statyczne i dynamiczne w grach stochastycznych z ciągłym zbiorem graczy

This paper is a study of a general class of stochastic games with an atomless measure space of players and an arbitrary time space. The payoffs of the players depend on their own strategy, the trajectory of the system and the function with values being finite dimensional statistics of static profiles. The players' available decisions depend on the trajectories of the system. The paper deals with relations between the static and dynamic equilibria as well as the existence of dynamic equilibria. The results are counterintuitive and much stronger than the results that can be obtained in games with finitely many players. An equivalence theorem is proven between the dynamic equilibrium (according to various definitions) and the family of static equilibria corresponding to it. Theorems on the existence of dynamic equilibria are shown as consequences. Theoretical results of the paper are illustrated by examples describing the exploitation of common ecological systems in which "the tragedy of the commons" appears.Artykuł przedstawia studium ogólnej klasy gier stochastycznych opisanych na ciągłych przestrzeniach graczy i dowolnych przestrzeniach czasu. Wypłaty graczy zależą od ich własnej strategii, trajektorii układu oraz funkcji o wartościach będących skończenie wymiarowymi statystykami profili statycznych. Dostępne graczom decyzje zależą od trajektorii układu. W artykule rozważa się zależności między rozwiązaniami (stanami równowagi) statycznymi i dynamicznymi, a także istnienie rozwiązań dynamicznych. Otrzymane wyniki są niezgodne z intuicją i znacznie silniejsze niż wyniki, jakie mogą być otrzymane dla gier ze skończoną liczbą graczy. Dowiedziono twierdzenia o równoważności między rozwiązaniem dynamicznym (według różnych definicji) a rodziną rozwiązań statycznych, odpowiadającą temu rozwiązaniu dynamicznemu. Wykazano następnie prawdziwość twierdzeń o istnieniu rozwiązań dynamicznych jako konsekwencję poprzedniego twierdzenia. Wyniki teoretyczne, przedstawione w artykule, zostały zilustrowane przy pomocy przykładów opisujących wykorzystanie wspólnych systemów zasobowych, w których pojawia się nadmierna eksploatacja w postaci tzw. "tragedy of the commons"

The operation of ecosystems and game theory. II. Cooperation.

Artykuł nie zawiera streszczeniaThe article contains no abstrac

Stock market as a dynamic game with continuum of players

This paper contains a game-theoretic model describing the behaviour of investors at a stock exchange. The model presented is developed to reflect the actual market microstructure. The players constitute a non-uniform continuum, differing, among others, by the planning horizon, the external flow of money which can be invested, formation of expectations about future prices, which, briefly, divides the investors into five substantially different groups. Prices are determined by orders and the equilibrating mechanism of the stock exchange. The mechanism presented is the actual single-price auction system used, in particular, at Warsaw Stock Exchange. One of the main issues are self-verifying beliefs. Results of numerical simulations of stock exchange based on the model are also included

Dyn. Games Appl.

This paper investigates the role played by cooperation for the sustainable harvesting of an ecosystem. To achieve this, a bio-economic model based on a multi-species dynamics with interspecific relationships and multi-agent catches is considered. A comparison between the non-cooperative and cooperative optimal strategies is carried out. Revisiting the Tragedy of Open Access and over-exploitation issues, it is first proved analytically how harvesting pressure is larger in the non-cooperative case for every species. Then it is examined to what extent gains from cooperation can also be derived for the state of the ecosystem. It turns out that cooperation clearly promotes the conservation of every species when the number of agents is high. When the number of agents remains limited, results are more complicated, especially if a species-by-species viewpoint is adopted. However, we identify two metrics involving the state of every species and accounting for their ecological interactions which exhibit gains from cooperation at the ecosystem scale in the general case. Numerical examples illustrate the mathematical findings