Research Database

In a simple, coherent, general equilibrium model it is demonstrated why stock market prices do not reflect costly but socially useless information.

According to the folklore of economics, game theory has failed. This paper argues that that is an incorrect interpretation of the game theory literature. When faced with a well-posed problem, game theory provides a solution. When faced with an ill-posed problem, game theory fails to provide a solution. This is, indeed, the best one can hope for from a method of analysis! Further, some suggestions are made for facing game theory with well-posed economic problems.

Long-term contracts are explained as equilibrium strategies of supergames. In the specific coherent general equilibrium model provided, limited mobility of labor, in the form of a fixed cost of moving, generates long-term contracts.

The qualitative dynamics of a discrete time version of a deterministic, continuous time, nonlinear macro model formulated by Haavelmo are fully characterized. Recently developed methods of symbolic dynamics and ergodic theory are shown to provide a simple, effective means of analyzing the behavior of the resulting one-parameter family of first-order, deterministic, nonlinear difference equations. A complex periodic and random "aperiodic" orbit structure dependent on a key structural parameter is present, which contrasts with the total absence of such complexity in Haavelmo's continuous time version. Several implications for dynamic economic modelling are discussed.

This paper explores some of the implications for econometric practice of the principle that people’s observed behavior will change when their constraints change. In dynamic contexts, a proper definition of people’s constraints includes among them laws of motion that describe the evolution of the taxes they must pay and the prices of the goods that they buy and sell. Changes in agents’ perceptions of these laws of motion (or constraints) will in general produce changes in the schedules that describe the choices they make as a function of the information that they possess. Until very recently, received dynamic econometric practice ignored this principle. The practice of dynamic econometrics should be changed so that it is consistent with the principle that people’s rules of choice are influenced by their constraints. This is a substantial undertaking, and involves major adjustments in the ways that we formulate, estimate, and simulate econometric models.

This paper describes methods for estimating the parameters of continuous time linear stochastic rational expectations models from discrete time observations. The economic models that we study are continuous time, multiple variable, stochastic, linear-quadratic rational expectations models. The paper shows how such continuous time models can properly be used to place restrictions on discrete time data. Various heuristic procedures for deducing the implications for discrete time data of these models, such as replacing derivatives with first differences, can sometimes give rise to very misleading conclusions about parameters. The idea is to express the restrictions imposed by the rational expectations model on the continuous time process of the observable variables. Then the likelihood function of a discrete-time sample of observations from this process is obtained. Estimators are obtained by maximizing the likelihood function with respect to the free parameters of the continuous time model.

Herein, it is demonstrated that the competitive provision of fiat money is generically either inefficient or infeasible.

The recurrent banking panics of the 19th century and the Great Depression of the 1930s are widely viewed as failures of our economic system. A simple version of Samuelson’s overlapping generations model is used to generate such failures of Walrasian equilibrium. The spontaneous “panics” generated involve a collapse of bank credit, causing in turn a drop in investment demand. The model suggests that both the recent technological advances in the intermediation industry and the current move towards deregulation of that industry are ominous developments.

This paper shows how the cross-equation restrictions delivered by the hypothesis of rational expectations can serve to solve the aliasing identification problem. It is shown how the rational expectations restrictions uniquely identify the parameters of a continuous time model from statistics of discrete time models.

A simple model of the process of learning in a diverse economy is presented. This model produces a stylized business cycle with shocks which precipitate the learning process. All agents have the same information, which implies that this business cycle cannot be reduced by improved information flow, counter to many models of output and employment fluctuation.

In this paper I describe a “monetary” system in which backing is provided for the government’s liabilities by way of contingent resort to taxes. The system has some of the features of a commodity money system with a large seignorage spread between bid and ask prices. It is studied within the context of a one-good, pure exchange model of two-period-lived overlapping generations in which, aside from various uniform boundedness assumptions, considerable diversity is allowed both within and across generations. Two results are established: (i) the existence of at least one perfect foresight competitive equilibrium, and (ii) the Pareto optimality of any such equilibrium.

Our suggestion consists of three postulates: assets are valued only in terms of their payoffs, perfect foresight, and complete and costless markets under laissez-faire. Together these postulates imply that the crucial anomaly, rate-of-return dominance of “money,” is to be explained by legal restrictions.

Our defense of these postulates is two-fold. First we compare them with existing alternative theories. Second, we provide an illustrative model which : (a) is consistent with the postulates, (b) implies rate-of-return dominance under suitable legal restrictions, and (c) addresses monetary policy questions with standard welfare economics and, in particular, rationalizes in terms of price discrimination a debt management policy that “tailors debt issues to the needs of the market.”

Theory typically does not give us reason to believe that economic models ought to be formulated at the same level of time aggregation at which data happen to be available. Nevertheless, this is frequently done when formulating econometric models, with potentially important specification-error implications. This suggests examining the alternatives, one of which is to model in continuous time. The primary difficulty in inferring the parameters of a continuous time model given sampled observations is the “aliasing identification problem.” This paper shows how the restrictions implied by rational expectations sometimes do, and sometimes do not, resolve the problem. This is accomplished very simply in the context of a hypothesis about the term structure of interest rates. The paper confirms and extends results obtained for another example by Hansen and Sargent.

A new approach to market behavior is suggested. This approach has a coherent game theoretic foundaton, addresses such anomalous economic behaviors as strikes, rigid wages and unemployment, regulation of financial markets, depresssion, and nonmarket allocation, and, more generally, provides insights for Finance, Oligopoly Theory, Industrial Organization, and Macroeconomics. The central theme of the approach is that exchange technologies are a basic building block in a model, as are tastes, endowments, and production technologies. Moreover, the key feature of an institution of exchange is that it allows the making of a binding final offer.

A model is presented in which demand deposits backed by fractional currency reserves and public insurance can be beneficial. The model uses Samuelson's pure consumption-loans model. The case for demand deposits, reserves, and deposit insurance rests on costs of illiquidity and incomplete information. The effect of deposit insurance depends upon how, and at what cost, the government meets its insurer's obligation--something which is not specified in practice. It remains possible that demand deposits and deposit insurance are a distortion, and reserve requirements serve only to limit the size of this distortion.

In this paper we consider a particular international economic policy regime: the laissez-faire regime, the distinguishing features of which are unrestricted portfolio choice and floating exchange rates. And as we show, that regime, although favored by many economists, is not economically feasible. It does not have a determinate equilibrium. That is an implication of an over-lapping-generations model. But as we argue in the paper, that is no reason for doubting the indeterminacy of the laissez-faire regime equilibrium.

A critical roadblock to modelling inventories of finished goods has been the claim that production and inventory decisions of a perfectly competitive firm are determined independently of each other. A basic goal of this study is to specify fundamental preferences of economic agents, technologies, constraints and market structures that are, in a rough way, capable of generating patterns of serial correlation and cross correlation between inventories and employment of factors of production that are consistent with those observed in the data. The claim is made that the time series for inventories, output and employment can be interpreted as emerging from a well specified dynamic, stochastic competitive equilibrium in which economic agents are assumed to form rational expectations about variables not included in their information sets. Inventories and employment will not be related in a direct way if and only if the price elasticity of demand for output is equal to infinity.

Game theory addresses a problem which is central to economics. Yet, according to the folklore of economics, game theory has failed. This paper argues that this is an incorrect interpretation of the game theory literature. When faced with a well-posed problem, game theory provides a solution. Procedures for facing game theory with well-posed problems are suggested, and examples of economic applications provided. The applications are Samuelson's fiat money model, Phelps' capital overaccumulation problem, multiple rational expectations equilibria, and a bargaining problem.

The qualitative dynamics of a discrete time version of a deterministic, continuous time, nonlinear macro model formulated by Haavelmo are fully characterized. The methods of symbolic dynamics and ergodic theory are shown to provide a simple, effective means of analyzing the behavior of the resulting one-parameter family of first-order, deterministic, nonlinear difference equations. A complex periodic and random "aperiodic" orbit structure dependent on a key structural parameter is present, which contrasts with the total absence of such complexity in Haavelmo's continuous time version. Several implications for dynamic economic modelling are discussed.