Finding a Nash equilibrium in spatial games is an NP-complete problem

Summary. We consider the class of (finite) spatial games. We show that the problem of determining whether there exists a Nash equilibrium in which each player has a payoff of at least k is NP-complete as a function of the number of players.Received: 15 September 2002, Revised: 9 March 2003, JEL Classification Numbers: C72.Correspondence to: H. HallerWe thank a referee for helpful comments. The hospitality of the Institute of Economics, University of Copenhagen, and the Institute for Advanced Studies, Vienna, is gratefully acknowledged by the third author.     

Sequencing and the Adding-up Property in Contingent Valuation of Endangered Species: Are Contingent Non-Use Values Economic Values?

This paper presents tests of the theoretical validity of the contingent valuation (CV) method. The validity of CV is especially a concern when involving environmental goods with a predominant non-use value. One test of theoretical validity is the adding-up property that implies that a specific good should be equally valued irrespectively of it is being valued directly or built-up sequentially. In this CV study four independent sub-samples stated willingness to pay for the same composite good, or package, using different sequences. One sub-sample valued the composite good directly, while two sub-samples faced built-up sequences valuing first subsets of this composite good. A fourth sub-sample valued the composite good from a dividing-out approach, facing first the valuation of a larger multi-package. Theoretically expected sequencing effects were observed; the subset goods obtained higher values earlier in a sequence, and the dividing-out approach decreased the stated value for the composite good. Most importantly, these CV data did pass the tests of the adding-up property.     

Strategic Regulation Policy in the Internet

Some countries are importers while others are exporters of global backbone connectivity. At the same time, input components such as local access are non-traded. This paper analyzes a non-cooperative regulatory game between importing and exporting countries, assuming that the prices of both traded and non-traded inputs can be regulated. We show that exporting countries choose a more restrictive regulation of non-traded goods than importing countries do. We further show that a requirement of international non-discrimination may hurt importing countries, and give firms producing traded inputs incentives to invest in quality degradation.     

Probleme gleichgewichtsorientierter Inflationserklärungen

Ohne ZusammenfassungHerrn Doz. Abele und Herrn Dr. Beinsen bin ich für die kritische Durchsicht dieser Arbeit zu Dank verpflichtet. Doz. Abele hat mir vor allem allgemeine Hinweise zum Stand der Theorie gegeben, die mich zu dieser Arbeit erst so recht anregten.     

Environmental quality indicators: Background,principles and examples from Norway

The need for a simple and general overview of the development in the state of the environment has led to work on environmental indicators in several countries and international organizations. Except for the basic common requirement of providing an overview, the works vary a great deal with regard to final aim, target groups, classification and, hence, choice of indicators. This paper gives an overview of the work carried out in the Central Bureau of Statistics of Norway within this field, with emphasis on the basic principles behind the choice of indicators. A hierarchical system of indicator sets is proposed, and examples of indicators are presented. Also, a brief overview of work carried out elsewhere is included.     

A theory of sequential reciprocity

Many experimental studies indicate that people are motivated by reciprocity. Rabin [Amer. Econ. Rev. 83 (1993) 1281] develops techniques for incorporating such concerns into game theory and economics. His theory is developed for normal form games, and he abstracts from information about the sequential structure of a strategic situation. We develop a theory of reciprocity for extensive games in which the sequential structure of a strategic situation is made explicit, and propose a new solution concept—sequential reciprocity equilibrium—for which we prove an equilibrium existence result. The model is applied in several examples, and it is shown that it captures very well the intuitive meaning of reciprocity as well as certain qualitative features of experimental evidence.     

Why Punish? Social reciprocity and the enforcement of prosocial norms

Recently economists have become interested in why people who face social dilemmas in the experimental lab use the seemingly incredible threat of punishment to deter free riding. Three theories with evolutionary microfoundations have been developed to explain punishment. We survey these theories and use behavioral data from surveys and experiments to show that the theory called social reciprocity in which people punish norm violators indiscriminately explains punishment best.JEL Classification: C91, C92, D64, H41 Correspondence to: Jeffrey P. CarpenterWe thank Carolyn Craven, Corinna Noelke and two referees for comments, and Middlebury College for financial assistance. In addition, Carpenter acknowledges the support of the National Science Foundation (SES-CAREER 0092953).