Nash equilibria equal competitive equilibria

With strictly monotone preferences and a continuum of traders, there is a game in which the set of Nash equilibria is exactly the same as the set of competitive equilibria.     

Walrasian equilibria as limits of noncooperative equilibria. Part II: Pure strategies

We examine the connection between Walrasian equilibria of a limit economy (with infinitesimal firms) and noncooperative (Cournot) equilibria of approximating finite economies (with significant firms). Nonconvex production sets, decreasing returns in the aggregate, and endogenous determination of the number of active firms are allowed. A Walrasian equilibrium is a limit of pure strategy noncooperative equilibria only if a condition (loosely analogous to downward sloping demand in the partial equilibrium constant returns to scale case) holds. The condition is also sufficient to guarantee the existence of a robust sequence of pure strategy noncooperative equilibria which converges to the Walrasian equilibrium.     

Ordinal vs cardinal status: Two examples

We demonstrate that in models where agents have concerns for status the model predictions can drastically change depending on whether status is modelled as an ordinal or cardinal magnitude. As a proof, we show that two well known theoretical findings are not robust to the substitution of ordinal status with cardinal status [Frank, R.H., The Demand for Unobservable and Other Positional Goods. American Economic Review, (75):101–116, 1985.] and viceversa [Clark, A. and Oswald, R.J., Comparison-Concave Utility and Following Behavior in Social and Economic Settings. Journal of Public Economics, (70):133–155, 1998.].     

Computing sequential equilibria using agent quantal response equilibria

The limit of any convergent sequence of agent quantal response equilibria is a sequential equilibrium of an extensive game. Using a logarithmic transformation of action probabilities, it is numerically feasible and practical to compute such sequences, and thereby compute good approximations to sequential equilibrium assessments. This paper describes the algorithm to compute the sequences, and outlines the convergence and selection properties of the method.     

Existence of perfect equilibria: a direct proof

We provide a direct proof of the existence of perfect equilibria in finite normal form games and extensive games with perfect recall. It is done by constructing a correspondence whose fixed points are precisely the perfect equilibria of a given finite game. Existence of a fixed point is secured by a generalization of Kakutani theorem, which is proved in this paper. This work offers a new approach to perfect equilibria, which would hopefully facilitate further study on this topic. We also hope our direct proof would be the first step toward building an algorithm to find the set of all perfect equilibria of a strategic game.     

Computing equilibria: a computational complexity perspective

Computational complexity is the subfield of computer science that rigorously studies the intrinsic difficulty of computational problems. This survey explains how complexity theory defines “hard problems”; applies these concepts to several equilibrium computation problems; and discusses implications for computation, games, and behavior. We assume minimal prior background in computer science.     

Ricardo on machinery: an analysis of Ricardo's examples

The examples that are reported in the famous chapter “On Machinery” added by Ricardo in the third edition of his Principles are reconstructed and analyzed. Two sets of assumptions that rationalize the examples presented by Ricardo are identified: a) the innovation concerns an agricultural commodity and does affect neither which land is marginal nor the technology applied on the marginal land; b) the innovation concerns a non-basic commodity. Ricardo was aware of these two facts and he seems to have used them respectively in the first and second of his examples.     

Revenue comparison in common-value auctions: Two examples

When players' affiliated values are symmetrically distributed, expected revenue in the second-price auction equals or exceeds that in the first-price auction (Milgrom and Weber, 1982). We provide two common-value examples where this ranking fails when players are asymmetrically informed.     

Existence of voting-market equilibria

We show the existence of an equilibrium in a model where private goods are allocated by markets and the public good (bad) is allocated by majority rule voting.     

On learning equilibria

Bullard (1994) and Schönhofer (1999) show that endogenous business cycles may emerge in an inflationary overlapping generations model where households predict future inflation rates by running a least squares regression on prices. We show that given the same beliefs but under an alternative, more natural, estimation procedure based upon inflation rates the monetary steady state will be globally stable for a large set of savings functions. We also study an evolutionary competition between the two estimation procedures. Although the dynamics are stabilized for a large set of parameter values, endogenous business cycles may still emerge in this heterogeneous beliefs framework.     

Coalition-proof Bertrand equilibria

Summary. This paper examines the coalition-proof Nash equilibria of a Bertrand model of price competition where firms supply all demand. When firms are asymmetric we prove existence and provide a sufficient condition for uniqueness. For symmetric firms, we show that an equilibrium is necessarily unique. We also examine whether this unique equilibrium outcome is implementable through a sequential move game where the firms take turns at announcing prices. Finally we examine the limiting property of such equilibria as the number of firms go to infinity.Received: 20 March 2002, Revised: 5 August 2003JEL Classification Numbers: D43, D41, L13.Correspondence to: Kunal SenguptaWe are deeply indebted to an anonymous referee for very helpful and incisive comments that led to substantial improvements in the paper. We also gratefully acknowledge the hospitality of the Department of Finance, Hong Kong University of Science and Technology where much of the work on this paper was carried out.     

Anonymous sequential games: Existence and characterization of equilibria

Summary In this paper we consider Anonymous Sequential Games with Aggregate Uncertainty. We prove existence of equilibrium when there is a general state space representing aggregate uncertainty. When the economy is stationary and the underlying process governing aggregate uncertainty Markov, we provide Markov representations of the equilibria.Table of notation Agents' characteristics space ( ) - A Action space of each agent (aA) - Y Y = x A - Aggregate distribution on agents' characteristics - (X) Space of probability measures onX - C(X) Space of continuous functions onX - _X Family of Borel sets ofX - State space of aggregate uncertainty ( ) - x _t=1 aggregate uncertainty for the infinite game - = (₁,₂,...,_t,...) - ^{t t} (₁, ₂,..., _t) - L₁(^t,C ×A),v _t Normed space of measurable functions from ^t toC( x A) - 8o(^t,( x A)) Space of measurable functions from ^tto( x A) - X^t X^t= x _s=1 ^t X - _X ^t Borel field onX ^t - v Distribution on - v_t Marginal distribution of v on ^t - v(^t)((¦^t)) Conditional distribution on given ^t - v^t(^s)(v_t(¦^s)) Conditional distribution on ^t given ^s (wheres) - _t Periodt distributional strategy - Distributional strategy for all periods =(₁,₂,...,_t,...) - _t Transition process for agents' types - ( _t,^t,y)(P _t+1(, _t , ^t ,y)) Transition function associated with _t - u _t Utility function - V _t (, a, , ^t) Value function for each collection (, a, , ^t ) - W _t (, , ^t ) Value function given optimal action a - C() Consistency correspondence. Distributions consistent with and characteristics transition functions - B() Best response correspondence (which also satisfy consistency) - E Set of equilibrium distributional strategies - x _t=1 ( ^t , (x A)) - S Expanded state space for Markov construction - (, a, ) Value function for Markov construction - P( _t ^* , _t y)(P(, _t ^* , _t , _y )) Invariant characteristics transition function for Markov game We wish to acknowledge very helpful conversations with C. d'Aspremont, B. Lipman, A. McLennan and J-F. Mertens. The financial support of the SSHRCC and the ARC at Queen's University is gratefully acknowledged. This paper was begun while the first author visited CORE. The financial support of CORE and the excellent research environment is gratefully acknowledged. The usual disclaimer applies.     

Barro-Gordon revisited: Reputational equilibria with inferential expectations

We incorporate inferential expectations into the Barro-Gordon model (Barro and Gordon, 1983a) of time inconsistency and consider reputational equilibria. The range of sustainable equilibria shrinks as the private sector becomes more belief-conservative.     

Robustness of sunspot equilibria

Summary. A sunspot equilibrium (SSE) is based on some extrinsic randomizing device (RD). We analyze the robustness of SSE. (1) We say that an SSE allocation is robust to refinements if it is also an SSE allocation based on any refinement of its RD. (2) We introduce two core concepts for analyzing the robustness of SSE in the face of cooperative-coalition formation. In the first, the blocking allocations are based on the RD that defines the SSE. In the second (stronger) core concept, coalitions select their own RDs. For the convex economy with restricted market participation, SSE allocations are robust under each of the definitions and the cores converge on replication of the economy to the set of SSE allocations. For the economy with an indivisible good, SSE allocations are not always robust. We provide examples of each of the following: (i) an SSE allocation that is not robust to refinement, (ii) an SSE allocation that is in neither core, (iii) an SSE allocation that is in the first core, but not in the second, and (iv) a core that does not converge upon replication to the set of SSE allocations. Received: July 31, 1995; revised version August 30, 1996     

On supply-constrained equilibria

The paper gives sufficient conditions for the existence of an equilibrium with price rigidities and quantity rationing where: (i) demand is never rationed; (ii) net trades of an a priori chosen numeraire are never rationed; and (iii) supply is rationed only when relative prices are downward rigid.     

Excess supply equilibria

This paper addresses a fundamental problem in economic theory: How can there be equilibria of the economic system where some commodity is in excess supply, yet that commodity's relative price shows no tendency to fall? Of course, the principal example of such a phenomenon is an economy experiencing a prolonged period of involuntary unemployment of the labor force during which there is no significant change in the real wage.In the following pages, I shall describe a two-commodity, general equilibrium model that has a continuum of unemployment equilibria, one for any given unemployment rate. The important feature of this model is that workers establish their wage rates in an attempt to maximize expected utility. The information upon which these wage setting decisions are based is provided by actual labor market transactions.Despite the voluntary nature of the wage setting decision, I shall argue that each equilibrium of this economy exhibits involuntary unemployment in the Keynesian sense. For there will always be another equilibrium with a lower real wage, a higher level of employment, and at which (at least when workers are risk neutral) each worker achieves a higher level of expected utility.