Existence and transversality conditions for a general ‘unbounded-horizon’ model of the mining firm

This paper derives conditions under which optimal programs exist for a general model of the competitive or monopolistic mining firm. The model significantly extends and synthesizes previous formulations by including both resource extraction and discoveries of new reserves, with stock-dependent resource exploitation costs and incomplete resource exhaustion, endogenous technical innovation, and state-dependent resource demand. In addition, the analysis addresses complications arising from having optimal programs defined over an ‘unbounded horizon’, with the possibility of either a finite or infinite terminal time and a non-zero terminal (‘salvage’) valuation if the terminal time is finite. The necessity of the infinite-horizon transversality conditions also is established. The paper illustrates a strongly intuitive approach to existence questions for infinite-horizon or unbounded-horizon control problems, with weaker concavity and interiority assumptions than are often encountered in the literature.     

Optimal control on an infinite time horizon: The turnpike approach

The optimal control problem with infinite horizon is defined. Under assumptions motivated by the theory of optimal economic growth the controllability of the system, the turnpike property, the asymptotic behavior and the existence of optimal trajectories are fully explored.     

Necessary conditions for infinite-horizon discounted two-stage optimal control problems

In many situations in Economics, one would like to analyse the optimal timing of switching between alternative and consecutive regimes. A natural framework for such an analysis seems to be one of multi-stage optimal control problems, where the switching instants between regimes are endogenously determined. The existing literature considers only the case of two-stage optimal control problems with finite horizon. However, in many cases, it seems more appropriate to consider a problem with an infinite horizon. By deriving the appropriate necessary conditions for such a problem we generalise the methodology in analysing endogenous regime switches.     

Existence of equilibria with infinitely many commodities: Banach lattices reconsidered

The purpose of this paper is twofold. The first aim is to present an extension of the results on the existence of Walrasian equilibrium to the infinite dimensional setting. The result depends on two crucial assumptions. These are the compactness of the collection of feasible allocations and the non-emptiness of the interior of the production set. The proof is a direct generalization of Bewley's (1972) proof for the L_∞ case. The second purpose of this paper is to show that the recent result of Mas-Colell (1986) on the existence of equilibrium for exchange economies on Banach lattices can be obtained through an argument based on the result outlined above. That is, exchange economies on Banach lattices with ‘uniformly proper’ preferences behave as though they were production economies in which the production sets have non-empty interior.     

Feasibility and optimality of the initial capital stock in the Ramsey vintage capital model

Using a discrete-time version of the Ramsey Vintage Capital Model we provide a characterization of the set of initial capital stocks compatible with a predefined scrapping time, given the rate of technical progress and the level of capital productivity. Each profile of initial capital stock in that set generates a complete infinite horizon feasible capital path. From that characterization, we prove the existence of a minimum value for the scrapping time of the machines compatible with the rate of technological progress. Moreover, for each level of capital productivity, there exists an upper bound for the technological progress which allows the existence of feasible capital paths with full employment. Finally, we transform the infinite horizon dynamic programming problem into one of finite dimension. We use this to find the optimal lifetime for the machines as well as the optimal composition of the initial capital stocks. A numerical example shows that, in accordance with the infinite horizon approach to the problem, the increase in the rate of technological progress leads to a decrease in optimal scrapping time of capital goods.     

Lagrange multipliers in infinite horizon discrete time optimal control models

We consider constrained optimization problems on the (non-reflexive) Banach Space of bounded sequences and derive sufficient conditions on the objective function and the constraints so that the Lagrangean can be represented by a summable sequence of multipliers. We apply our results to a discrete time infinite horizon control model of the type that arises in economics, and show how our methods can be applied to analyze the existence of bounded solutions.     

Optimal investment with vintage capital: Equilibrium distributions

The paper concerns the study of equilibrium points, or steady states, of economic systems arising in modeling optimal investment with vintage capital, namely, systems where all key variables (capitals, investments, prices) are indexed not only by time but also by age. Capital accumulation is hence described as a partial differential equation (briefly, PDE), and equilibrium points are in fact equilibrium distributions in the variable of ages. A general method is developed to compute and study equilibrium points of a wide range of infinite dimensional, infinite horizon, optimal control problems. We apply the method to optimal investment with vintage capital, for a variety of data, deriving existence and uniqueness of equilibrium distribution, as well as analytic formulas for optimal controls and trajectories in the long run. The examples suggest that the same method can be applied to other economic problems displaying heterogeneity. This shows how effective the theoretical machinery of optimal control in infinite dimension is in computing explicitly equilibrium distributions. To this extent, the results of this work constitute a first crucial step towards a thorough understanding of the behavior of optimal paths in the long run.     

Investment and pricing strategies of competing firms: A computational approach

We analyze the classical investment and pricing problem of a dominant firm faced with competition from substitute industries or marginal firms in the same field. The firm owns a finite level of a resource (e.g. the stock of an exhaustible one), the consumption of which is to be divided optimally over a finite planning horizon. The competitors' measures affect the demand for the resource towards the dominating firm. Rising crude oil prices and investments in forms of alternative energy are representative examples of the strategic questions which involve competitive and contradictory interests among firms within an industry. The investment and pricing problem can be solved analytically only with strong, simplifying assumptions. To make the analysis simpler and to relax these restrictions, we combine a series of numerical tools, computerize them, and build up a user-oriented, computerized decision aid, which we call a ‘computerized approach’. We solve the problem under different sets of theoretical assumptions. This chosen incremental theory building allows us to study the theoretical sensitivity of the original problem.     

On durable goods monopolies and the Coase-Conjecture

Consider the durable goods monopoly game with uniformly distributed consumers' valuations. To establish the Coase-Conjecture in this context takes an infinite time horizon and a negligible delay between market rounds. An infinite time horizon or patience of market participants alone are not sufficient for the Coase-Conjecture, nor is an arbitrarily small delay between price offers within a finite time horizon. Received: 20 March 1996 / Accepted: 15 December 1997     

Beyond the Global City Concept and the Myth of ‘Command and Control’

The article argues that the lack of convincing empirical evidence for the global economy as being subject to ‘command and control’ results from that contention being a neo‐Marxist myth. First, imagining the global economy as being subject to ‘highly concentrated command’ through the function of some major cities as ‘strategic sites’ for the production of ‘command and control’ is traced back through several neo‐Marxist authors to narrate its genesis, and to argue that the lack of evidence for that proposition is a consequence of those antecedents envisioning capitalism as a totalizing structure, thus making the assumption that it is subject to control and coordination from a distance. Second, Taylor's interlocking world city network model is forensically examined to explain that it is fallacious because it is a structuralism that, bedevilled by a sorites paradox, contains the further problem of containing no credible evidence for the existence of ‘command centres’. Finally, the article moves beyond neo‐Marxism's key concepts by juxtaposing their assumptions with ethnographic results from social studies of finance, a manoeuvre which forges an understanding of cities as socio‐technical assemblages and eventful multiplicities, beyond, inter alia, the baseless assumption that the global economy is subject to ‘command and control’.     

On the existence of equilibria in economies with an infinite dimensional commodity space

We prove an infinite dimensional extension of the Gale–Nikaido–Debreu lemma which includes all necessary limiting processes and allows a proof of the existence of equilibria under standard assumptions in an economy with infinitely many commodities which exactly parallels the proof of Debreu (1959) for the finite dimensional case.     

Optimal agglomerations in dynamic economics

We study rational expectations equilibrium problems and social optimum problems in infinite horizon spatial economies in the context of a Ramsey type capital accumulation problem with geographical spillovers. We identify sufficient local and global conditions for the emergence (or not) of optimal agglomeration, using techniques from monotone operator theory and spectral theory in infinite dimensional Hilbert spaces. We show that agglomerations may emerge, with any type of returns to scale (increasing or decreasing) and with the marginal productivity of private capital increasing or decreasing with respect to the spatial externality. This is a fairly general result indicating the importance of the network structure of the spatial externality relative to the properties of the aggregate production function. Our analytical methods can be used to systematically study optimal potential agglomeration and clustering in dynamic economics.     

Treatment of Fixed Capital in the Sraffian Framework and in the Theory of Dynamic Input–Output Models

This paper is concerned with a comparison of the treatment of fixed capital in some multi-sectoral models. First, the dynamic Leontief model is investigated. Scrutiny shows that this model suffers from conceptual misconceptions which result from restrictive assumptions concerning full-capacity production and the transferability of capital in place, and from the definition of technical coefficients. Whereas most input–output (IO) models are based on the assumption of infinite life of fixed capital, the Sraffian concept is to treat used fixed capital items as ‘intermediate’ goods, which appear as joint products until they are worn out. To compare that approach with some IO models, an application of the concept of a ‘plant’ is provided. Finally, it is demonstrated that Leontief's model, as well as some recent generalizations, are special cases of a Sraffa-von Neumann type of model.     

Frequency Domain Tests for Residual Serial Correlation in Cointegration Regressions

This paper introduces tests for residual serial correlation in cointegrating regressions. The tests are devised in the frequency domain by using the spectral measure estimates. The asymptotic distributions of the tests are derived and test consistency is established. The asymptotic distributions are obtained by using the assumptions and methods that are different from those used in Grenander and Rosenblatt (1957) and Durlauf (1991). Small-scale simulation results are reported to illustrate the finite sample performance of the tests under various distributional assumptions on the data generating process. The distributions considered are normal and t-distributions. The tests are shown to have stable size at sample sizes as large as 50 or 100. Additionally, it is shown that the tests are reasonably powerful against the ARMA residuals. An empirical application of the tests to investigate the ‘weak-form’ efficiency in the foreign exchange market is also reported.     

The intrinsic comparative dynamics of locally differentiable feedback Nash equilibria of autonomous and exponentially discounted infinite horizon differential games

The comparative dynamics of locally differentiable feedback Nash equilibria are derived for the ubiquitous class of autonomous and exponentially discounted infinite horizon differential games. The resulting refutable implications are intrinsic to the said class of differential games, and thus form their basic, empirically testable, properties. Their relationship with extant results in the optimal control theory and the static game theory is discussed. Separability conditions are identified on the instantaneous payoff and transition functions under which the intrinsic comparative dynamics collapse, in form, to those in optimal control problems. Applications of the results to capital accumulation and sticky-price games are provided.     

Efficient equilibria in a differential game of capitalism

One considers a differential game of capitalism ‘à la Lancaster’. Feedback Nash equilibria and Pareto optimal solutions are characterized under the assumption that the planning horizon is infinite. It is then shown that, by combining a Pareto optimal solution with the Nash feedback equilibrium strategy pair, which plays the role of a threat, one can obtain an efficient equilibrium which is also subgame perfect in the sense of Selten. This result modifies sensibly the previous interpretation of the inherent inefficiency of capitalism.     

Behavioral equilibrium and evolutionary dynamics in asset markets

This paper analyzes a dynamic stochastic equilibrium model of an asset market based on behavioral and evolutionary principles. The core of the model is a non-traditional game-theoretic framework combining elements of stochastic dynamic games and evolutionary game theory. Its key characteristic feature is that it relies only on objectively observable market data and does not use hidden individual agents’ characteristics (such as their utilities and beliefs). A central goal of the study is to identify an investment strategy that allows an investor to survive in the market selection process, i.e., to keep with probability one a strictly positive, bounded away from zero share of market wealth over an infinite time horizon, irrespective of the strategies used by the other players. The main results show that under very general assumptions, such a strategy exists, is asymptotically unique and easily computable.     

The solution of the infinite horizon tracking problem for discrete time systems possessing an exogenous component

In this paper we derive an algorithm that yields, for a discrete-time system, a control minimizing a quadratic cost functional. The system considered is linear and possesses an exogenous component. The cost functional is a quadratic tracking equation over an infinite time horizon with positive semi-definite weighting matrices such that a weighted sum of these matrices is positive definite. The infinite planning horizon Minimum Variance cost criterion and the Linear Quadratic regulator are special cases. For stabilizable systems we give a characterization of the asymptotically admissible reference trajectories.     

Incentive compatibility constraints and dynamic programming in continuous time

This paper is devoted to the study of infinite horizon continuous time optimal control problems with incentive compatibility constraints that arise in many economic problems, for instance in defining the second best Pareto optimum for the joint exploitation of a common resource, as in Benhabib and Radner [Benhabib, J., Radner, R., 1992. The joint exploitation of a productive asset: a game theoretic approach. Economic Theory, 2: 155–190]. An incentive compatibility constraint is a constraint on the continuation of the payoff function at every time. We prove that the dynamic programming principle holds, the value function is a viscosity solution of the associated Hamilton–Jacobi–Bellman (HJB) equation, and that it is the minimal supersolution satisfying certain boundary conditions. When the incentive compatibility constraint only depends on the present value of the state variable, we prove existence of optimal strategies, and we show that the problem is equivalent to a state constraints problem in an endogenous state region which depends on the data of the problem. Some economic examples are analyzed.     

Existence and monotonicity of solutions to moral hazard problems

This paper provides a method to prove existence of solutions to some moral hazard problems with infinite set of outcomes. The argument is based on the concept of nondecreasing rearrangement and on a supermodular version of Hardy–Littlewood’s inequality. The method also provides qualitative properties of solutions. Both the cases of wage contracts and of insurance contracts are studied.