Long-run equilibria, dominated strategies, and local interactions

The present note revisits a result by Kim and Wong (2010) showing that any strict Nash equilibrium of a coordination game can be supported as a long run equilibrium by properly adding dominated strategies. We show that in the circular city model of local interactions the selection of 1/2 -dominant strategies remains when adding strictly dominated strategies if interaction is decentral". Conversely, if the local interaction structure is central" by adding properly suited dominated strategies any equilibrium strategy of the original game can be supported as long run equilibrium. Classification- JEL: C72, D83

Constrained Interactions and Social Coordination

We consider a co-evolutionary model of social coordination and network formation whereagents may decide on an action in a 2 x 2- coordination game and on whom to establish costly links to. We find that a payoff dominant convention is selected for a wider parameter range when agents may only support a limited number of links as compared to a scenario where agents are not constrained in their linking choice. The main reason behind this result is that constrained interactions create a tradeoff between the interactions an agent has and those he would rather have. Further, we discuss convex linking costs and provide suffcient conditions for the payoff dominant convention to be selected in mxm coordination games.

Sequential Search with Incompletely Informed Consumers: Theory and Evidence from Retail Gasoline Markets

A large variety of markets, such as retail markets for gasoline or mortgage markets, are characterized by a small number of firms offering a fairly homogenous product at virtually the same cost, while consumers, being uninformed about this cost, sequentially search for low prices. The present paper provides a theoretical examination of this type of market, and confronts the theory with data on retail gasoline prices. We develop a sequential search model with incomplete information and characterize a perfect Bayesian equilibrium in which consumers follow simple reservation price strategies. Firms strategically exploit consumers being uninformed about their production cost, and set on average higher prices compared to the standard complete information model. Thus, consumer welfare is lower. Using data on the gasoline retail market in Vienna (Austria), we further argue that incomplete information is a necessary feature to explain observed gasoline prices within a sequential search framework.

Imitation and the Evolution of Walrasian Behavior: Theoretically Fragile but Behaviorally Robust

A well-known result by Vega-Redondo (1997) implies that in symmetric Cournot oligopoly, imitation leads to the Walrasian outcome where price equals marginal cost. In this paper, we show that this result is not robust to the slightest asymmetry in fixed costs. Instead of obtaining the Walrasian outcome as unique prediction, every outcome where agents choose identical actions will be played some fraction of the time in the long run. We then conduct experiments to check this fragility. We obtain that, contrary to the theoretical prediction, the Walrasian outcome is still a good predictor of behavior.evolutionary game theory, stochastic stability, imitation, Cournot markets, information, experiments, simulations

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

Local Interactions and Switching Costs

We study the impact of switching costs on the long run outcome in 2 x 2 coordination games played in the circular city model of local interactions. For low levels of switching costs the predictions are in line with the previous literature and the risk dominant convention is the unique long run equilibrium. For intermediate levels of switching costs the set of long run equilibria still contains the risk dominant convention but may also contain conventions that are not risk dominant. For high levels of switching costs also non-monomorphic states will be included in the set of long run equilibria. Finally, we reconcile our result with a recent paper by Norman (2009) by considering the case of large interaction neighborhoods in large populations

Price Dispersion, Search Externalities, and the Digital Divide

We propose a model of price competition where consumers exogenously differ in the number of prices they compare. Our model can be interpreted either as a non–sequential search model or as a network model of price competition. We show that i) if consumers who previously just sampled one firm start to compare more prices all types of consumers will expect to pay a lower price and ii) if consumers who already sampled more than one price sample (even) more prices then there exists a threshold –the digital divide– such that all consumers comparing fewer prices than this threshold will expect to pay a higher price whereas all consumers comparing more prices will expect to pay a lower price than before.

Imitation and the Evolution of Walrasian Behavior: Theoretically Fragile but Behaviorally Robust

A well-known result by Vega-Redondo implies that in symmetric Cournot oligopoly, imitation leads to the Walrasian outcome where price equals marginal cost. In this paper we show that this result is not robust to the slightest asymmetry in fixed costs. Instead of obtaining the Walrasian outcome as unique prediction, every outcome where agents choose identical actions will be played some fraction of the time in the long run. We then conduct experiments to check this fragility. We obtain that, contrary to the theoretical prediction, the Walrasian outcome is still a good predictor of behavior.Evolutionary game theory; Stochastic stability; Imita- tion; Cournot markets; Information; Experiments; Simulations

Imitation and the Evolution of Walrasian Behavior: Theoretically Fragile but Behaviorally Robust

A well-known result by Vega-Redondo implies that in symmetric Cournot oligopoly, imitation leads to the Walrasian outcome where price equals marginal cost. In this paper we show that this result is not robust to the slightest asymmetry in fixed costs. Instead of obtaining the Walrasian outcome as unique prediction, every outcome where agents choose identical actions will be played some fraction of the time in the long run. We then conduct experiments to check this fragility. We obtain that, contrary to the theoretical prediction, the Walrasian outcome is still a good predictor of behavior.

A network model of price dispersion

We analyze a model of price competition á la Bertrand in a network environment. Firms only have a limited information on the structure of network: they know the number of potential customers they can attract and the degree distribution of customers. This incomplete information framework stimulates the use of Bayesian-Nash equilibrium. We find that, if there are customers only linked to one firm, but not all of them are, then an equilibrium in randomized strategies fails to exist. Instead, we find a symmetric equilibrium in randomized strategies. Finally, we test our results on US gasoline data. We find empirical evidence consistent with firms playing random strategies