Finitely Many Players with Bounded Recall in Infinitely Repeated Games

We study the set of limit points of equilibrium payoffs in n-player repeated games, with bounded recall, when the memory capacities of all the players grow to infinity. Two main issues are explored: (i) whether differential information enables players to play correlatively, and (ii) the extent to which boundedly rational players can learn others′ behavior patterns and conceal their own. Journal of Economic Literature Classification Number: 026.     

A Robust Folk Theorem for the Prisoner's Dilemma

We prove the folk theorem for the Prisoner's dilemma using strategies that are robust to private monitoring. From this follows a limit folk theorem: when players are patient and monitoring is sufficiently accurate, (but private and possibly independent) any feasible individually rational payoff can be obtained in sequential equilibrium. The strategies used can be implemented by finite (randomizing) automata. Journal of Economic Literature Classification Numbers: C72, C73, D82.     

Using or hiding private information? An experimental study of zero-sum repeated games with incomplete information

This paper studies the value of private information in strictly competitive interactions in which there is a trade-off between (i) the short-run gain of using information, and (ii) the long-run gain of concealing it. We implement simple examples from the class of zero-sum repeated games with incomplete information. While the empirical value of information does not always coincide with the theoretical prediction, the qualitative properties of the value of information are satisfied in the laboratory: (i) it is never negative, (ii) it decreases with the number of repetitions, (iii) it is bounded below by the value of the infinitely repeated game, and (iv) it is bounded above by the value of the one-shot game. In line with the theory, the empirical use of private information is almost complete when it should be, and decreases in longer interactions.     

Learning with bounded memory in games

We study learning with bounded memory in zero-sum repeated games with one-sided incomplete information. The uninformed player has only a fixed number of memory states available. His strategy is to choose a transition rule from state to state, and an action rule, which is a map from each memory state to the set of actions. We show that the equilibrium transition rule involves randomization only in the intermediate memory states. Such randomization, or less frequent updating, is interpreted as a way of testing the opponent, which generates inertia in the player's behavior and is the main short-run bias in information processing exhibited by the bounded memory player.     

Non-computable strategies and discounted repeated games

Summary A number of authors have used formal models of computation to capture the idea of bounded rationality in repeated games. Most of this literature has used computability by a finite automaton as the standard. A conceptual difficulty with this standard is that the decision problem is not closed. That is, for every strategy implementable by an automaton, there is some best response implementable by an automaton, but there may not exist any algorithm forfinding such a best response that can be implemented by an automaton. However, such algorithms can always be implemented by a Turing machine, the most powerful formal model of computation. In this paper, we investigate whether the decision problem can be closed by adopting Turing machines as the standard of computability. The answer we offer is negative. Indeed, for a large class of discounted repeated games (including the repeated Prisoner's Dilemma) there exist strategies implementable by a Turing machine for whichno best response is implementable by a Turing machine.The work was begun while Nachbar was a visitor at The Center for Mathematical studies in Economics and Management Science at Northwestern University; he is grateful for their hospitality. We are also grateful to Robert Anderson and Neil Gretsky and to seminar audiences at UCLA for useful comments, and to the National Science Foundation and the UCLA Academic Senate Committee on Research for financial support. This paper is an outgrowth of work reported in Learning and Computability in Discounted Supergames.     

The politics of progressive income taxation with incentive effects

This paper studies majority voting over quadratic taxation and investigates under which conditions marginal progressivity emerges as a voting outcome. In our model with endogenous income, there is no majority (Condorcet) winning tax schedule. We then investigate less demanding political equilibrium concepts in order to see under which conditions the set of equilibria is composed only of progressive tax functions. We follow three strategies: (i) reduction of the policy space to the tax functions that are ideal for some voter; (ii) elimination of weakly dominated strategies and the use of mixed strategies in a standard Downsian two-party competition game; (iii) assumption that political parties interact repeatedly and care about the size of their majority. Although each approach captures a different aspect of political behavior, they point to the same (simulation-based) conclusion that progressivity is more likely to emerge for most distributions of abilities and that it is actually the only possible voting outcome if the distribution is sufficiently concentrated at the middle.     

Nash Equilibrium and Welfare Optimality

If A is a set of social alternatives, a social choice rule (SCR) assigns a subset of A to each potential profile of individuals' preferences over A , where the subset is interpreted as the set of "welfare optima". A game form (or "mechanism") implements the social choice rule if, for any potential profile of preferences, (i) any welfare optimum can arise as a Nash equilibrium of the game form (implying, in particular, that a Nash equilibrium exists) and, (ii) all Nash equilibria are welfare optimal. The main result of this paper establishes that any SCR that satisfies two properties—monotonicity and no veto power—can be implemented by a game form if there are three or more individuals. The proof is constructive.     

NONPARAMETRIC MODELS OF FINANCIAL LEVERAGE DECISIONS

This paper applies nonparametric decision tree models to the analysis of financial leverage decisions. This approach presents three appealing features: (i) the relationship between leverage and explanatory variables is not predetermined but is derived from information provided by the data, (ii) the models respect the fractional nature of leverage ratios, and (iii) each covariate is allowed to influence in different ways the financial leverage decisions of firms automatically assigned to different groups. Based on a data set of Portuguese firms, decision trees are used to tackle both classification (the decision to issue debt) and regression (the decision on the amount of debt to be issued, conditional on using debt) problems. It is found that: (i) two‐part models are the most appropriate specification for explaining the overall amount of debt used by firms, (ii) there are no drastic differences between the results produced by tree and parametric models, although some divergences may arise, and (iii) tree models suggest relationships between covariates and leverage that parametric models fail to capture, especially when the sample size is small.     

Information structures in optimal auctions

A seller wishes to sell an object to one of multiple bidders. The valuations of the bidders are privately known. We consider the joint design problem in which the seller can decide the accuracy by which bidders learn their valuation and to whom to sell at what price. We establish that optimal information structures in an optimal auction exhibit a number of properties: (i) information structures can be represented by monotone partitions, (ii) the cardinality of each partition is finite, (iii) the partitions are asymmetric across agents. We show that an optimal information structure exists.     

DYNAMIC WELFARE COST OF STAGNATION: AN ALTERNATIVE MEASURE TO THE LUCAS–OBSTFELD MODEL

The present paper proposes an alternative measure to the Lucas–Obstfeld model to analyze the welfare costs of stagnation, and provides a practical illustration of both the Lucas–Obstfeld model and the alternative model. Compared with the Lucas–Obstfeld model, the alternative model can evaluate: (i) whether policy was implemented in a timely fashion; (ii) whether the policy cost was expensive compared with the cost of stagnation; and (iii) whether the policy implemented was effective or whether an additional policy is required.     

Asynchronous Choice and Markov Equilibria

We provide a theoretical foundation for the use of Markov strategies in repeated games with asynchronous moves. If admissible strategies must display finite (arbitrarily long) memory and each player incurs a “complexity cost” which depends on the memory length required by her strategy, then every Nash equilibrium must be in Markovian strategies. If, in addition, admissible strategies have uniformly bounded memory, every rationalizable strategy must be Markovian. These results are robust to considerations of perfection and also yield interesting implications for equilibrium selection in simple contexts. Journal of Economic Literature Classification Numbers: C72, C73.     

Edgeworth's conjecture with infinitely many commodities: commodity differentiation

Summary. Convergence of the cores of finite economies to the set of Walrasian allocations as the number of agents grows has long been taken as one of the basic tests of perfect competition. The present paper examines this test in the most natural model of commodity differentiation: the commodity space is the space of nonnegative measures, endowed with the topology of weak convergence. In Anderson and Zame [12], we gave counterexamples to core convergence in L ¹, a space in which core convergence holds for replica economies and core equivalence holds for continuum economies; in addition, we gave a core convergence theorem under the assumption that traders' utility functions exhibit uniformly vanishing marginal utility at infinity. In this paper, we provide two core convergence results for the commodity differentiation model. A key technical virtue of this space is that relatively large sets (in particular, closed norm-bounded sets) are compact. This permits us to invoke a version of the Shapley-Folkman Theorem for compact subsets of an infinite-dimensional space. We show that, for sufficiently large economies in which endowments come from a norm bounded set, preferences satisfy an equidesirability condition, and either (i) preferences exhibit uniformly bounded marginal rates of substitution or (ii) endowments come from an order-bounded set, core allocations can be approximately decentralized by prices. Received: July 29, 1996; revised version: January 14, 1997     

Effort maximization in asymmetric contest games with heterogeneous contestants

Contest rules are set up by administrators who frequently have discretionary power in specifying the details of these rules, i.e., they can bias the contest rules toward specific contestants in order to further their prime objective. We derive the optimal bias of the contest rule for a contest administrator, who is interested in maximizing the total efforts expended in the contest. The solution is obtained in closed form for a widely used class of n-person contest games. Setting the optimal bias has important implications: (i) there is never exclusion of strong players, instead there is (endogenously induced) inclusion of weak contestants; (ii) the contest administrator will optimally level the playing field by encouraging weak contestants, but he will not equalize the contestants’ chances unless they are identical; and (iii) at least three contestants will be active in equilibrium of the optimal contest, irrespective of heterogeneity.     

When sunspots don't matter

Summary We show that a finite, competitive economy isimmune to sunspots if (i) preferences are strictly convex, (ii) the set of feasible allocations is convex, and (iii) the contingent-claims market is perfect. The conditions (i)–(ii) cover some, but not all, economies with nonconvex technologies. Based on an indivisible-good example, we show that even economies with strictly convex preferences and full insurance arenot in general immune from sunspots. We also show that (1) the sufficient conditions (i)–(iii) are not necessary for sunspot immunity and (2)ex-ante efficiency is not necessary for immunity from sunspots.This paper is based on an earlier paper, Indivisibilities in Production, and Sunspot Equilibrium, presented at the 1990 S.E.D.C. Meetings, Minneapolis-St. Paul, June 1990. The research support of NSF Grant SES-9012780, the Center for Analytic Economics, and the Thorne Fund is gratefully acknowledged.     

Farsightedly stable networks

A set of networks G is pairwise farsightedly stable (i) if all possible farsighted pairwise deviations from any network g∈ G to a network outside G are deterred by the threat of ending worse off or equally well off, (ii) if there exists a farsighted improving path from any network outside the set leading to some network in the set, and (iii) if there is no proper subset of G satisfying conditions (i) and (ii). A non-empty pairwise farsightedly stable set always exists. We provide a full characterization of unique pairwise farsightedly stable sets of networks. Contrary to other pairwise concepts, pairwise farsighted stability yields a Pareto dominant network, if it exists, as the unique outcome. Finally, we study the relationship between pairwise farsighted stability and other concepts such as the largest pairwise consistent set and the von Neumann–Morgenstern pairwise farsightedly stable set.     

Measuring the gains from trade under monopolistic competition

Abstract .  Three sources of gains from trade under monopolistic competition are (i) new import varieties available to consumers; (ii) enhanced efficiency as more productive firms begin exporting and less productive firms exit; (iii) reduced markups charged by firms due to import competition. The first source of gains can be measured as new goods in a CES utility function for consumers. We argue that the second source is formally analogous to the producer gain from new goods, with a constant-elasticity transformation curve for the economy. We suggest that the third source of gain can be measured using a translog expenditure function for consumers, which, in contrast to the CES case, allows for finite reservation prices for new goods and endogenous markups.     

Dynamic control of a monopolist’s product and process innovation with reference quality

ABSTRACT

Our main purpose is to investigate the dynamic control problem of a monopolist’s product and process innovation under reference quality. The main features of this article are: (i) a monopolist dealing with customer behaviour in the spirit of the principle of behaviour economics determines the product price, and carries out the activities of product and process innovation; (ii) the consumers’ demand depends on price, product quality and reference quality, and adopts an additive separable demand function form. Our main results show that under the cases of the monopolist optimum and the social planner optimum, (i) there exists an unique stable, which is a saddle-point steady-state equilibrium; (ii) the change rates of the monopolist’s investments in product and process innovation are increasing with the reference quality, while the monopolist’s steady-state investments in product and process innovation are decreasing with the reference quality; (iii) as the memory parameter increases with other parameters kept constant, it is very likely that the monopolist’s investment in process innovation be greater than the investment in product innovation; and (iv) the social incentive towards both investments in product and process innovation is always larger than the private incentive characterizing the profit-seeking monopolist.     

Expectations and the housing market: A model of house price dynamics

We examine the characteristics of housing markets under adaptive and heterogeneous expectations. Model agents have finite horizons, and their borrowings are constrained by the collateral value of housing stock. Our model shows that expectation-driven housing price dynamics constantly change the direction of movement. The steady-state process of housing prices follows an endogenous oscillation process, and the magnitude of the cycles can be amplified by external shocks. Our quantitative results imply that (i) short-term positive and long-term negative serial correlations in housing price changes are inherent, (ii) house prices and expected house price movements are positively correlated, and (iii) fluctuations in housing prices are not fully explained by fundamentals.     

Revisiting the economics of climate change: the role of geoengineering

Technically simple measures to directly reduce mean global temperatures could be available in the near future. We introduce “geoengineering” into a simple analytical model of climate change. We model the technical and economic characteristics of geoengineering in line with the recent literature from physical and environmental management sciences. We investigate: (i) under which circumstances geoengineering can substitute, partly or completely, for traditional abatement strategies, (ii) under which conditions and at what level geoengineering is optimally employed, and (iii) whether geoengineering can mitigate free-riding problems.     

The nonatomic assignment model

Summary We formulate a model with a continuum of individuals to be assigned to a continuum of different positions which is an extension of the finite housing market version due to Shapley and Shubik. We show that optimal solutions to such a model exist and have properties similar to those established for finite models, namely, an equivalence among the following: (i) optimal solutions to the linear programming problem (and its dual) associated with the assignment model; (ii) the core of the associated market game; (iii) the Walrasian equilibria of the associated market economy.