Correlated equilibrium and sunspot equilibrium

Summary We show by an example that the sunspot equilibria of a competitive economy are not equivalent to the correlated equilibria if sunspots generate transfers between (extrinsic) states of nature (through a contingent commodities market). Nevertheless, we prove that the sunspot equilibrium allocations of a standard overlapping generations economy coincide with the (strategic form) correlated equilibrium allocations of a natural market game mimicking the economy.     

Note on the non-existence of sunspot equilibrium

In this note, we emphasize the role of consumers’ risk aversion in the non-existence of sunspot equilibria in incomplete market economies. We prove that there are no sunspot equilibria if the fundamentals of the underlying economy admit a unique equilibrium for any distribution of endowments. This substantiates Mas-Colell’s (Economic analysis of markets and games: essays in honor of Frank Hahn. MIT, Cambridge, 1992) conjecture. We also prove that, in a two-consumer economy, no sunspot equilibrium exists under the more relaxed condition that the underlying economy admits a unique equilibrium for the initial endowment. This is a generalization of Corollaries 1 and 2 of Hens and Pilgrim (Econ Theory 24:583–602, 2004).      

Ergodic chaos in optimal growth models with low discount rates

Summary We show that for every discount factor(0,1) one can find infinitely many strictly concave discrete-time optimal growth models in reduced form which have optimal policy functions exhibiting ergodic chaos. These reduced form models are interpreted in a two-sector optimal growth setting with utility functions depending on consumption as well as on capital.We thank Luigi Montrucchio for pointing out an error in a previous version of the paper.     

Adaptive learning in extensive form games and sequential equilibrium

Summary. This paper studies adaptive learning in extensive form games and provides conditions for convergence points of adaptive learning to be sequential equilibria. Precisely, we present a set of conditions on learning sequences such that an assessment is a sequential equilibrium if and only if there is a learning sequence fulfilling the conditions, which leads to the assessment. Received: November 5, 1996; revised version: May 28, 1997     

Excess demand functions, equilibrium prices, and existence of equilibrium

Summary. For continuous aggregate excess demand functions of economies, the existing literature (e.g. Sonnenschein (1972, 1973), Mantel (1974), Debreu (1974), Mas-Colell (1977), etc.) achieves a complete characterization only when the functions are defined on special subsets of positive prices. In this paper, we allow the functions to be defined on a larger class of price sets, (allowing, for example the closed unit simplex, including its boundary). Besides characterizing excess demands for a larger class of economies, our extension provides a useful tool for proving other results. It allows us to characterize the equilibrium price set for a larger class of economies. It also permits extending Uzawa's observation (1962), by showing that Brouwer's Fixed-Point Theorem is implied by the Arrow-Debreu Equilibrium Existence Theorem (1954, Theorem I). Received: October 18, 1995; revised version June 28, 1996     

Short-sighted managers and learnable sunspot equilibria

This paper assumes that firm managers make choices over a finite horizon while households plan over an infinite horizon. Following Shea (2013), I assume that labor exhibits firm-specific learning by doing so that newly employed labor is less productive than experienced labor. In the model, optimization requires that firm managers make conjectures about how their choices affect the labor demand choices of their successors. The model yields two steady states; one where the firm manager behaves as if she cares only about the present period and another where she is forward looking. The former (myopic) steady state usually exhibits higher output than the non myopic steady state. The non-myopic steady state also exhibits two regions of indeterminacy where extraneous, self-fulfilling expectational errors add volatility. One of these regions of indeterminacy is usually stable under adaptive learning while the other never is stable under learning.     

Manipulation of endowments and sunspot equilibria

We study the connection between occurrence of manipulation via reallocating endowments by coalitions and sunspot equilibria. The uncertainty about which coalition will form introduces extrinsic uncertainty into the economy. Under certain conditions, manipulation of endowments by coalitions can occur if and only if sunspots matter. We would like to thank Bill Ethier, Atsushi Kajii, Cuong Le Van, Karl Shell, Koji Shimomura, Nicholas Yannelis, an anonymous referee, as well as seminar participants at the Second Asian General Equilibrium Theory Workshop, 2005, Tokyo; Workshop on Uncertainty and Information, IMS, NUS, 2005; Kobe Institute of Economic Research; Public Economic Theory 2005 Conference, Marseille; and the South and South East Asia Econometric Society Meetings, 2006, Chennai for helpful discussions and comments.     

Optimal chaos,nonlinearity and feasibility conditions

Summary This study constructs a class of dynamic models in which optimal paths are generated by nonlinear transition functions similar to a tent map. We provide a sufficient condition under which such a transition function is a chaotic map. This characterization provides a way to construct complex nonlinear dynamics in a broad range of dynamic economic models.We would like to thank Michele Boldrin, William Brock, Richard Day, Mukul Majumdar, Lionel McKenzie, Tapan Mitra, Luigi Montrucchio, Jose Scheinkman, Rangarajan Sundaram and the referees for comments and discussions.     

Environmental sustainability, nonlinear dynamics and chaos

Summary. This paper studies the possibility of nonlinear dynamics in a simple overlapping generations model with the environment – the John-Pecchenino (1994) model. We show that if people's concerns towards greener preferences and the maintenance efficiency relative to degradation are not sufficiently high, cyclically or chaotically fluctuating equilibria are more likely to exist; moreover, under a specific condition, a complicated topological structure might emerge. Our short-run analysis complements John and Pecchenino's long-run analysis and our findings suggest that the associated transition towards an environmentally sustainable state is not trivial. Received: September 10, 1996; revised version: October 2, 1997     

Substitute goods, auctions, and equilibrium

This paper identifies two notions of substitutes for auction and equilibrium analysis. Weak substitutes, the usual price-theory notion, guarantees monotonicity of tâtonnement processes and convergence of clock auctions to a pseudo-equilibrium, but only strong substitutes, which treats each unit traded as a distinct good with its own price, guarantees that every pseudo-equilibrium is a Walrasian equilibrium, that the Vickrey outcome is in the core, and that the “law of aggregate demand” is satisfied. When goods are divisible, weak substitutes along with concavity guarantees all of the above properties, except for the law of aggregate demand.     

Diversity, persistence and chaos in consumption patterns

In this paper we present a model from which discretionary consumption dynamics can be analyzed as global properties emerging from the endogenous transformation of a society inhabited by boundedly rational interactive consumers. By considering local and global interactions among consumers, we show that behavioral diversity plays a central role in the evolution of consumption patterns. The analysis of the model reveals the existence of a regime characterized by the persistence of different social standards, and a time evolution of the social distribution of behavioral patterns towards a heteroclinic cycle. In some cases the evolution seems to be chaotic, generating unpredictable, erratic dynamics of the aggregate social indices (average or social propensity for discretionary consumption).      

A dynamic general equilibrium model of pollution abatement under learning by doing

In 2013, Beladi et al. constructed a dynamic general equilibrium model of pollution, and characterized a steady-state equilibrium. In this paper, we extend Beladi et al.’s model to an even more general model in which the pollution abatement costs under learning by doing are taken into account. In our model, the instantaneous abatement costs depend on both the rate of abatement and the experience of using a technology. Our objective is to apply optimal control theory to investigate the dynamic general equilibrium model of pollution abatement, and derive the steady-state equilibrium properties and optimal levels of emission permits and pollution treatment.     

Schumpeterian growth,chaos, and the formation of dissipative structures

This paper reformulates several basic ideas introduced by Joseph Schumpeter to examine the correlation between productivity growth and technological change in order to explore why American productivity growth has been sluggish for the past two decades. Convetional growth theory maintains that a primary cause of low productivity growth is inadequate capital formation, which in turn is caused by low private domestic saving. This paper borrows concepts from cybernetics, formal information theory, and chaotic dynamic systems to describe the Schumpeterian process through which innovative “new combinations” of capital goods generate wealth, productivity increases, and income growth, and which in turn cause increased savings. It describes the process through which such fundamental technological changes are diffused by entrepreneurs throughout the economy, and concludes that the fundamental causes of America's relatively weak productivity growth are to be found in policies or practices that inhibit innovation and entrepreneurship.     

学习型组织、学习型领导、学习力

21世纪是知识经济时代,在知识经济时代,成功只代表着过去,能力代表着今天,学习力代表着未来。个人要成为学习者,企业要成为学习型组织,国家要成为学习型社会。新世纪企业领导的主要任务是领导企业的员工更好的学习,提高企业的学习能力,学习型组织的领导者也有了新的角色定位,领导者是设计师、仆人和教师。员工素质和水平提高了,领导的水平更应该提高,提高的一个主要途径就是提升学习力。一个具有学习能力的人,就是一个不断走向成功的人。21世纪成功的关键是要进行有效的学习,即爱学、会学才会赢。每家企业都会有不同的“学习途径”,可谓条条道路通罗马。     

Rationalizable expectations and sunspot equilibria in an overlapping-generations economy

There are two theories for the treatment of market uncertainty: rationalizable expectations and sunspot equilibria. This paper shows how the game-theoretic solution concept of rationalizable expectations can be applied to an overlapping-generations exchange economy. Some general properties of these equilibria are discussed. It is shown that rationalizable-expectations equilibria are the predictions yielded by considering sunspot equilibria in which probability beliefs may differ across individuals. This result allows for a new interpretation of sunspot equilibria and helps to understand their relevance.     

Ambiguity,uncertainty aversion and equilibrium welfare

Summary. In order to analyse the effect of ambiguity and uncertainty aversion on equilibrium welfare, a two period, pure exchange one good economy is considered. Agents are Choquet-expected-utility maximizers with same convex capacity and strictly concave utility index. It is proven that equilibrium is indeterminate whenever several probabilities in the core of the capacity minimize the expected value of aggregate endowment and not all agents have same expected endowments under those probabilities. It is further shown that small changes in aggregate endowment may have drastic welfare implications. A more general model is considered in the case of no aggregate uncertainty: agents have a set of priors and are uncertainty averse as modelled by Gilboa-Schmeidler [1989]. In the case of complete markets, it is shown that assets have a spread of equilibrium prices similar to the spread of no-arbitrage prices compatible with absence of arbitrage in markets with imperfections.Received: 2 June 2000, Revised: 27 March 2003, JEL Classification Numbers: D46, D59,D60, G12.I have benefited from conversations with L. Epstein, F. Magnien and J. M. Tallon.     

General equilibrium, wariness and efficient bubbles

Wary consumers overlook gains but not losses in remote sets of dates or states. As preferences are upper but not lower Mackey semi-continuous, Bewley?s (1972) [4] result on existence of equilibrium whose prices are not necessarily countably additive holds. Wariness is related to lack of myopia and to ambiguity aversion (and, therefore, to Bewley?s (1986) [6] work on Knightian uncertainty). Wary infinite lived agents have weaker transversality conditions allowing them to be creditors at infinity and for bubbles to occur in positive net supply assets completing the markets. There are efficient allocations that can only be implemented with asset bubbles.     

Reputation, control rights and game equilibrium

Using the reputation model of Kreps (1982), Vickers (1986) and Barro(1986), we develop a dynamic game model with incomplete information to examine the relations between the managers of state-owned enterprises(SOEs) in China and the government as the enterprise’s owner. Employing the model, we show that even a noncoopertive manager will not intrude the owner’s interests until the last period of his term in order to maximize his long term utility. The paper also discusses some phenomenona in state-owned enterprises in China, such as “insiders’ control”, “59 phenomenon” and excess on-the-job consumption.      

Rationing rule, imperfect information and equilibrium

Summary. The impact of imperfect information on the price setting behaviour of firms is analysed. Specifically, consumers support an information cost to become informed about prices. Firms are endowed with U-shaped average cost curves. If a firm does not supply more than its competitive supply as determined by its marginal cost schedule, then we show that the existence of a pure strategy equilibrium is conditional on the rationing rule employed. If uninformed consumers are served first then the monopoly price is the sole equilibrium whenever consumers' information costs are high enough. Otherwise, a pure strategy equilibrium fails to exist contrary to the results of Salop and Stiglitz (1977) or Braverman (1980) who implicitly suppose that firms supply all the demand at a given price. Received: May 17, 1999; revised version: September 15, 2000     

Investment,interest rate rules,and equilibrium determinacy

Summary. By adding endogenous investment to a flexible-price, money-in-the-utility-function model, this paper studies the role that physical capital plays in stabilizing the real side of the economy when the monetary authority follows interest-rate feedback rules. We show that with inelastic labor supply equilibrium uniqueness is ensured under both active and passive monetary policies. For the case where money affects both preferences and technology, the uniqueness result remains true under active monetary policy. With endogenous labor supply, the uniqueness result holds again regardless of the stance of monetary policies for the case with separable leisure, but indeterminacy remains likely under both active and passive monetary policies when leisure is nonseparable.Received: 19 December 2001, Revised: 12 May 2003, JEL Classification Numbers: E52, O42.We are grateful to Jess Benhabib and an anonymous referee for helpful comments and suggestions. Correspondence to: C.K. Yip