A cost-benefit analysis of moose harvesting in Scandinavia. A stage structured modelling approach

A cost-benefit analysis of moose (Alces alces) harvesting in Scandinavia is presented within the framework of an age structured model with four categories of animals (calves, yearlings, adult females, and adult males). The paper aims to demonstrate the economic content of such a wildlife model and how this content may change under shifting economic and ecological conditions. Two different harvesting regimes are explored: landowner profit maximization, where the combined benefit of harvesting value and browsing damage is taken into account, and overall management, where the costs and damages of moose-vehicle collisions are taken into account as well. An empirical analysis of the Norwegian moose stock indicates that the present stock level is far too high compared with the overall management scenario, and that the composition of the harvest could be improved.     

Markov perfect Nash equilibria in models with a single capital stock

Many economic problems can be formulated as dynamic games in which strategically interacting agents choose actions that determine the current and future levels of a single capital stock. We study necessary as well as sufficient conditions that allow us to characterise Markov perfect Nash equilibria for these games. These conditions can be translated into an auxiliary system of ordinary differential equations that helps us to explore stability, continuity and differentiability of these equilibria. The techniques are used to derive detailed properties of Markov perfect Nash equilibria for several games including voluntary investment in a public capital stock, the inter-temporal consumption of a reproductive asset and the pollution of a shallow lake.     

On the regime-switching and asymmetric dynamics of economic growth in the OECD countries

This study estimates the SETAR and STAR models and examines the regime-switching and asymmetric dynamics of economic growth for a comprehensive set of 10 OECD countries. The SETAR models of both Tsay and Hansen consistently reject the null hypothesis of linearity against the alternative hypothesis of threshold nonlinearity for all the sample countries. The STAR model reinforces the evidence and rejects the null hypothesis of linearity against STAR nonlinearity for all the sample countries, except Italy. The sequential F tests for the nested nulls suggest LSTAR nonlinearity for Austria, Japan, Korea, Mexico, Netherlands and New Zealand, and ESTAR nonlinearity for Finland, Germany and Norway. The forecast evaluations suggest that the SETAR models of Tsay and Hansen perform better, as compared to the AR, ARMA and STAR models. The forecasting performance of the STAR model is approximately similar to the forecasting performance of the linear AR and ARMA rivals. The persistence of lower regimes (with negative-growth or moderate-expansions) necessitates the need for the adoption of expansionary economic policies. While the longer durations of upper regimes (with positive-growth or fast-expansions) support the sustainability of the expansionary economic policies, the adequate precautions need to be taken for the inflationary implications of these policies.     

Stock return predictability: the role of inflation and threshold dynamics

This paper argues that the nature of stock return predictability varies with the level of inflation. We contend that the nature of relations between economic variables and returns differs according to the level of inflation, due to different economic risk implications. An increase in low level inflation may signal improving economic conditions and lower expected returns, while the opposite is true with an equal rise in high level inflation. Linear estimation provides contradictory coefficient values, which we argue arises from mixing coefficient values across regimes. We test for and estimate threshold models with inflation and the term structure as the threshold variable. These models reveal a change in either the sign or magnitude of the parameter values across the regimes such that the relation between stock returns and economic variables is not constant. Measures of in-sample fit and a forecast exercise support the threshold models. They produce a higher adjusted R², lower MAE and RMSE and higher trading related measures. These results help explain the lack of consistent empirical evidence in favour of stock return predictability and should be of interest to those engaged in stock market modelling as well as trading and portfolio management.     

Evolutionary Drift and Equilibrium Selection

This paper develops an approach to equilibrium selection in game theory based on studying the learning process through which equilibrium is achieved. The differential equations derived from models of interactive learning typically have stationary states that are not isolated. Instead, Nash equilibria that specify different out-of-equilibrium behaviour appear in connected components of stationary states. The stability properties of these components can depend critically on the perturbations to which the system is subjected. We argue that it is then important to incorporate such drift into the model. A sufficient condition is provided for drift to create stationary states, with strong stability properties, near a component of equilibria. Applications to questions of forward and backward induction are developed.     

Boundedness and nonlinearities in public debt dynamics: A TAR assessment

This study aims to investigate the dynamics of public debts over more than four decades for two of the main developed countries: the USA and the UK. To do this, we apply nonlinearity tests and threshold models. While the first tests enable us to check for further changes in the data, threshold models are required to assess the switching-regime hypothesis and to apprehend the main changes in public debts through different regimes. Our results provide several interesting findings. First, for both countries, we noted several structural breaks associated with well-known economic downturns, oil shocks, debt crises and financial crashes. Second, public debt dynamics seem to be characterized by various threshold effects that can improve the modeling and forecasting of public debt evolution. It is important to note that public debts vary significantly according to the regime and that a regime can be induced by specific macroeconomic factors. Keeping a close eye on such factors may help economists and policymakers to better control future public debt evolutions.     

Computation of non-linear continuous optimal growth models: experiments with optimal control algorithms and computer programs

In this paper we discuss the use of optimal control methods for computing non-linear continuous optimal growth models. We have discussed various recently developed algorithms for computing optimal control, involving step-function approximations, Runge–Kutta solutions of differential equations, and we suggest that the discretization approach is preferable to methods which solve first-order optimality conditions. We have surveyed some powerful computer programs by : , and for computing such models numerically. These programs have no substantial optimal growth modelling applications yet, although they have numerous engineering and scientific applications. A computer program named by is developed in this study. Results are reported for computing the Kendrick–Taylor optimal growth model using and programs based on the discretization approach. References are made to the computational experiments with and . The results are used to compare and evaluate mathematical and economic properties, and computing criteria. While several computer packages are available for optimal control problems, they are not always suitable for particular classes of control problems, including some economic growth models. The -based and , however, offer good opportunities for computing continuous optimal growth models. It is argued in this paper, that optimal growth modellers may find that these recently developed algorithms and computer programs are relatively preferable for a large variety of optimal growth modelling studies.     

A demographic-economic explanation of political stability: Mauritius as a microcosm

"This paper examines current models of economic and political development--social modernization theory, political and economic characteristics of stable regimes, and cross country analysis of political stability--and tests them on the Indian Ocean Island of Mauritius. The analysis continues with a causal explanation for political stability in Mauritius' recent history, derived from an examination of economic policies and demographic patterns. Political change in Mauritius over the past sixty years seems to be explained best by a model for political stability which integrates specific economic and demographic factors. The model, applicable to development in other third world nations, revises Malthus' conclusion that population and economic conditions move in an oscillatory relationship and replaces it with a more comprehensive theory, suggesting that political stability is a function of both economic development and a repeating cyclical relationship between economics and population."     

A program for algebraic and qualitative comparative statics and stability analysis

This paper presents a computer program designed by the author which determines algebraically and qualitatively both short- and long-run comparative statics multipliers for standard linear or linearized economic models. When the model is dynamic, i.e., when it involves linear of linearized differential equations, the program also provides the algebraic expressions and the qualitative signs for the coefficients of the characteristic polynomial.     

Analysis of the Lotka-Volterra competition equations as a technological substitution model

This paper provides insight into the dynamics of the Lotka-Volterra competition (LVC) equations, a much used competition model, and compares the dynamics of LVC competitive substitution to that of several well-known substitution models. The behavior of the LVC equations is analyzed for the special case of a dominant competitor at equilibrium being replaced after the introduction of a small population of an invading competitor with a competitive advantage. Expressions are derived that describe the growth of the invading competitor and that growth is shown to be of four classes: left asymmetric, logistic, right asymmetric with 1−ε₂ asymptote and right asymmetric with γ asymptote. It is shown that the LVC model reverts to logistic substitution in a market of fixed size, a result with important implications. The LVC equations are fitted to the Gompertz, Bass, Non-Symmetrical Responding Logistic (NSRL) and Sharif-Kabir substitution models and compared using a novel graphical technique. The LVC equations can reasonably mimic the full range of curve shapes exhibited by each of these models.     

On optimal steady states of n-sector growth models when utility is discounted

This paper contains results on local and global stability of n-sector growth models when utility is discounted mostly for small rates of discount. It is well known that when future utility is not discounted one can prove precise results about optimal steady states (OSS's) under fairly general assumptions. In particular, existence, uniqueness, and turnpike properties have been established by several authors. The counter examples presented by Kurz, Sutherland, and Weitzman, however, show that when utility is discounted, additional assumptions are required to obtain turnpike results. In general, it would be interesting to know how the submanifolds of stability change as δ changes. One hopes that certain conditions on the utility function would be sufficient to “classify” the submanifolds of stability and instability. Such a question is apparently very difficult to answer, but we think that the results obtained here will help in this task.The proof that the turnpike theorem holds for discount factors near one is divided in two parts. First, we prove that optimal paths “visit” neighborhoods of the modified OSS's. Then, we prove that local stability holds for such neighborhoods.In order to show this fact, we must prove that the local “stable manifold” varies continuously with the discount factor. This roundabout method is necessary since our problem is similar to proving uniform continuity with respect to a parameter of solutions of a differential equation in a noncompact interval of time.Other problems analyzed here include uniqueness and continuity of OSS's. We also discuss the relation between the saddle-point property and the local stability of infinite horizon optimal growth paths.     

Coevolution of economic and ecological systems

This paper analyzes a model of economy–environment coevolution in which economic activities induce the genetic evolution of a biological species. This model is applied to the problem of pesticide resistance management. Just as in Munro (Environ Resour Econ, 9:429–449, 1997), we consider three main types of interactions: (1) a large pest population reduces economic revenues, (2) economic activities select for resistant genes and (3) the spread of resistant genes affects the size of the pest population. The model differs from Munro in that it includes evolutionary modeling of economic strategies. Economic agents are assumed to be boundedly rational, i.e they cannot compute the optimal level of pesticide use that minimizes resistance among pests. Economic evolution represents the change in the distribution of pesticide strategies in the population of economic agents and is modeled by a replicator dynamics equation. The interactions between economic evolution of pesticide strategies, pest population dynamics and genetic evolution of resistance of pests are studied in a system of three differential equations. We explore the dynamics and stability properties of the system using numerical simulations.     

Institutional transformation and the origins of world income distribution

This paper presents an attempt to quantify institutional changes and examine the respective effects of de jure and de facto political institutions on the path of long-run economic growth and development for a large panel of countries in the period 1810–2000. Using factor analysis, latent indices of de jure and de facto political institutions are constructed by exploiting several existing institutional datasets. The empirical evidence consistently suggests that societies with more extractive political institutions in Latin America, South Asia, Middle East and Eastern Europe have achieved systematically slower long-run economic growth and failed to catch-up with the West. The evidence confirms the primacy of de facto institutional differences over de jure institutions in causing differential growth and development outcomes over time. It also explains why highly concentrated political power and extractive political regimes inhibited the path of economic growth by setting persistent barriers to the engagement in collective action. In the long run, institutional differences account for up to two thirds of within-country development path and up to 83% of between-country development gaps.     

Economies of scale and the optimality of rotational dynamics in forestry

Forest harvesting is traditionally analyzed in terms of the Faustmann rotation model. This paper considers the identification of optimal forest harvest regimes using jump controls. This approach enables the structural assumptions of clear-cut technology and identical cycles in perpetuity which are imposed in a Faustmann model to be relaxed. Jump control models permit investigation of the biological and economic conditions which favour continuous growth management regimes as opposed to clear-cut harvest regimes. A numerical solution approach to the jump control model is presented. The link between the harvest cost function and the optimal biomass path is analyzed. Economies of scale are shown to generate rotational harvest as optimal policies.      

The Southampton econometric model

Four reasons are offered for presenting a paper on a now defunct model. First it was one of the very few attempts to construct a large-scale econometric model of the UK. Second, is its monetary sector — few models of that vintage had such a sector and, unlike modern models, its monetary sector was strictly Keynesian. Third is the explicit modelling of output and price equations. And fourth is the treatment of disequilibrium. Disequilibrium arises through the incompatibility of plans: total demand, for example, may exceed total supply and profits may be exceptionally high or unsustainably low. The rest of the paper gives a fuller account of the role of these disequilibrium terms in the explanation of price and output changes. Lists of equations and working papers are attached.     

Market structure and matching with contracts

Ostrovsky (2008) [9] develops a theory of stability for a model of matching in exogenously given networks. For this model a generalization of pairwise stability, chain stability, can always be satisfied as long as agents' preferences satisfy same side substitutability and cross side complementarity. Given this preference domain I analyze the interplay between properties of the network structure and (cooperative) solution concepts. The main structural condition is an acyclicity notion that rules out the implementation of trading cycles. It is shown that this condition and the restriction that no pair of agents can sign more than one contract with each other are jointly necessary and sufficient for (i) the equivalence of group and chain stability, (ii) the core stability of chain stable networks, (iii) the efficiency of chain stable networks, (iv) the existence of a group stable network, and (v) the existence of an efficient and individually stable network. These equivalences also provide a rationale for chain stability in the unrestricted model. The (more restrictive) conditions under which chain stability coincides with the core are also characterized.     

Growth with many agents and wages paid ex ante

In this paper, we consider a one-sector model of economic growth with several infinitely-lived heterogeneous agents, who are endowed with diverse discount factors as well as preferences over consumption. In line with the classical Ramsey model, agents are not allowed to borrow against future income. Unlike the traditional assumption of ex post wage payment, wages are paid ex ante in our model. We first explain the difference between the assumptions of wages being paid ex ante and wages being paid ex post in the framework of a simple illustrative two-class model. Our main result shows that in contrast to the many-agent Ramsey model with ex post wage payment, the capital stock sequence converges to the steady state stock irrespective of production technology employed by the firms. Further, all impatient agents own zero capital stock, whereas the most patient agent owns the entire capital stock from some time onward. Thus, we have shown that a slight modification in the timing of wage payment in growth models can lead to significant changes in the stability properties of equilibrium dynamics.     

When is multidimensional screening a convex program?

A principal wishes to transact business with a multidimensional distribution of agents whose preferences are known only in the aggregate. Assuming a twist (= generalized Spence-Mirrlees single-crossing) hypothesis, quasi-linear utilities, and that agents can choose only pure strategies, we identify a structural condition on the value b(x,y) of product type y to agent type x — and on the principal?s costs c(y) — which is necessary and sufficient for reducing the profit maximization problem faced by the principal to a convex program. This is a key step toward making the principal?s problem theoretically and computationally tractable; in particular, it allows us to derive uniqueness and stability of the principal?s optimal strategy — and similarly of the strategy maximizing the expected welfare of the agents when the principal?s profitability is constrained. We call this condition non-negative cross-curvature: it is also (i) necessary and sufficient to guarantee convexity of the set of b-convex functions, (ii) invariant under reparametrization of agent and/or product types by diffeomorphisms, and (iii) a strengthening of Ma, Trudinger and Wang?s necessary and sufficient condition (A3w) for continuity of the correspondence between an exogenously prescribed distribution of agents and of products. We derive the persistence of economic effects such as the desirability for a monopoly to establish prices so high they effectively exclude a positive fraction of its potential customers, in nearly the full range of non-negatively cross-curved models.     

When are two-stage and three-stage least squares estimators identical?

Necessary and sufficient conditions are derived for the numerical equivalence of the two-stage and three-stage least squares estimators in a linear simultaneous equations model. The conditions are easy to verify in any practical application.