An Integrated Dynamic Model of Road Traffic Congestion Based on Simple Car-Following Theory: Exploring Hypercongestion

This paper presents a dynamic version of the standard static economic model of road traffic congestion, based on car-following theory. It is proven formally and illustrated numerically that the “hypercongested” equilibria found in the standard model are dynamically unstable. For arrival rates of users below the road's maximum capacity, the model reproduces the non-hypercongested stationary state outcomes found in the standard model. When the arrival rate exceeds this maximum capacity, however, the model produces outcomes consistent with Vickrey's model of bottleneck congestion. The model thus offers an integration and a generalization of these two archetype models.     

Age-specific dynamic labor demand and human capital investment

To study the optimal age-specific labor demand and human capital investment at the firm level we extend the standard dynamic labor demand model by introducing ‘age’ as a second dynamic variable and distinguish between two types of workers: ‘low skilled’ and ‘high skilled’. Applying an age-structured optimal control model we derive qualitative features of the optimal age-specific hiring and training effort. For the case of a linear revenue and production function we prove that firms do not anticipate changes in adjustment costs in their optimal decisions. This result no longer holds if a nonlinear revenue or production function is considered.     

Linear-quadratic approximation, external habit and targeting rules

We examine the linear-quadratic approximation of nonlinear dynamic stochastic optimization problems. A discrete-time version of Magill [1977a. A local analysis of N-sector capital accumulation under uncertainty. Journal of Economic Theory 15(2), 211–219] is generalized to models with forward-looking variables paying special attention to second-order conditions. This is the ‘large distortions’ case in the literature. We apply the approach to monetary policy in a DSGE model with external habit in consumption. We then develop a condition for ‘target-implementability’, a concept related to ‘targeting rules’. Finally, we extend the approach to a comparison between cooperative and non-cooperative equilibria in a two-country model and show that the ‘small distortions’ approximation is inappropriate for this exercise.     

The ‘science’ and ‘practice’ of HRM in small firms

This paper looks at the ‘science’ and ‘practice’ of human resource management in small firms. While there is growing evidence that the practice of human resource management in small firms is characterized by informality, there is less evidence about the science, or explaining why this is the case. We look to writing on strategic human resource management, which has at its heart the resource based view of the firm, for possibilities offered to understanding the science of human resource management in small firms.     

Aggregate stock market behavior and investors’ low risk aversion

This paper studies whether investors’ high risk aversion can be avoided in a representative-agent model that is able to explain aggregate stock market behavior in the US financial market. We present a consumption-based asset pricing model with a representative agent who has a ‘catching up with the Joneses’ preference to show that high risk aversion can be avoided in a representative-agent model that can help explain many of the empirically observed properties of the aggregate stock market return, including the equity premium and risk-free rate puzzles, the predictability of long-horizon stock returns, and the ‘leverage effect’ in return volatility.     

A theoretical comparison of the opportunity and gravity models

This paper compares the opportunity model with the gravity model from a theoretical view- point. First, based on a reexamination of Schneider's model, the ‘perceived opportunity model’ is proposed as a generalization of Schneider's model. Second, the similarity of the opportunity and gravity models is examined. In particular the condition of the opportunity model behaving like the gravity model is presented. Third, the difference of these models is investigated in terms of certain general model-theoretic properties. The behavioral ‘sensitivity’ of each model to spatial configuration changes is revealed by these properties.     

A behavioural model of traffic congestion: Endogenizing speed choice, traffic safety and time losses

Conventional economic models of traffic congestion assume that the relation between traffic flow and speed is a technical one. This paper develops a behavioural model of traffic congestion, in which drivers optimize their speeds by trading off time costs, expected accident costs and fuel costs. Since the presence of other drivers affects the latter two cost components and hence the Nash equilibrium speed, a ‘behavioural’ speed-flow relationship results for which external congestion costs include expected accident costs and fuel costs, in addition to the time costs considered in the conventional model. It is demonstrated that the latter in fact even cancel in the calculation of optimal congestion tolls. The overall welfare optimum in our model is found to be off the speed-flow function, and off the average and marginal cost functions derived from it in the conventional approach. This full optimum requires tolls to be either accompanied by speed policies, or to be set as a function of speed. Using an empirically calibrated numerical simulation model, we illustrate these qualitative findings, and attempt to assess their potential empirical relevance.     

Dynamic programming for non-additive stochastic objectives

We derive the existence of an optimum and the techniques of dynamic programming for non-additive stochastic objectives. Our key assumption for non-negative objectives is that asymptotic impatience exceeds asymptotic ‘mean’ growth, where ‘mean’ growth is derived not only from intertemporal inelasticity and the random return on investment but also from the curvature of the non-additive stochastic aggregator (i.e. the ‘certainty equivalent’). We provide broad families of new, interesting, and tractable examples. They illustrate that ‘mean’ growth can exist even when the distribution of returns has unbounded support, that power discounting often implies infinite asymptotic impatience, and that non-positive objectives are easily handled with few restrictions on growth.     

Benchmark priors for Bayesian model averaging

In contrast to a posterior analysis given a particular sampling model, posterior model probabilities in the context of model uncertainty are typically rather sensitive to the specification of the prior. In particular, ‘diffuse’ priors on model-specific parameters can lead to quite unexpected consequences. Here we focus on the practically relevant situation where we need to entertain a (large) number of sampling models and we have (or wish to use) little or no subjective prior information. We aim at providing an ‘automatic’ or ‘benchmark’ prior structure that can be used in such cases. We focus on the normal linear regression model with uncertainty in the choice of regressors. We propose a partly non-informative prior structure related to a natural conjugate g-prior specification, where the amount of subjective information requested from the user is limited to the choice of a single scalar hyperparameter g_0j. The consequences of different choices for g_0j are examined. We investigate theoretical properties, such as consistency of the implied Bayesian procedure. Links with classical information criteria are provided. More importantly, we examine the finite sample implications of several choices of g_0j in a simulation study. The use of the MC³ algorithm of Madigan and York (Int. Stat. Rev. 63 (1995) 215), combined with efficient coding in Fortran, makes it feasible to conduct large simulations. In addition to posterior criteria, we shall also compare the predictive performance of different priors. A classic example concerning the economics of crime will also be provided and contrasted with results in the literature. The main findings of the paper will lead us to propose a ‘benchmark’ prior specification in a linear regression context with model uncertainty.     

The latin model of welfare: Do ‘insertion contracts’ reduce long-term dependence?

This paper aims to present an assessment of the welfare policies implemented in most South European countries. Welfare programs in these countries try to combine a basic level of economic protection and measures favoring life and labor skills (‘insertion benefits’) of low-income households. We focus on a specific program set up with the twofold strategy of cash and ‘insertion benefits’ (Madrid's IMI) and, more precisely, on the so-called ‘insertion projects’, consisting in a gradual mix of job search assistance, training and subsidized jobs. We evaluate the effects of these ‘insertion projects’ on welfare recidivism and the duration of off-welfare spells using propensity score-matching methods. Our results suggest that propensity score estimators appear to reduce selectivity due to non-random participation. Both recidivism rates as well as the duration of off-welfare spells suggest potentially successful interventions.     

Export restraints in a model of trade with capital accumulation

This paper examines the impact of voluntary export restraints (VERs) in an international duopoly modeled as a differential game. With a Ramsey capital accumulation dynamics, the game admits multiple steady states, and a VER cannot be ‘voluntarily’ employed by the foreign firm in case of Cournot behavior in demand substitutes. Hence, the dynamic framework confirms the results of the VERs literature with static interaction in output levels. In the case of price behavior, the adoption of an export restraint may increase the profits of both firms if products are substitutes and the steady state is ‘market-driven’. However, contrary to the acquired wisdom based upon the static approach, the dynamic analysis also admits an equilibrium outcome, identified by the Ramsey golden rule, where the incentive to adopt a VER is ruled out, irrespective of whether firms are quantity- or price-setters.     

On the asymptotic behavior of stochastic economic processes : Two examples from intertemporal allocation under uncertainty

Some of the recently developed models to deal with economic problems involving uncertainty are based on simplifying assumptions on the nature of the stochastic law of the environment influencing economic decisions. Relying on the theory of martingales, we derive some general results on the asymptotic behavior of two dynamic processes that are of interest in the theory of intertemporal resource allocation. The first example is related to the ‘turnpike’ theory of optimal allocation. The second is addressed to the question of allocation of a scarce resource by using prices when the supply of the resource is random.     

Two planar facility location problems with high-speed corridors and continuous demand

The planar minisam (‘median’) and minimax (‘center’) facility location problems are examined under the assumptions that: demand is continuously and uniformly distributed: the L₁ (right-angle) metric is in use; and the planar region is traversed by a high-speed corridor (highway) running parallel to one of the directions of travel. For the minisum problem in a rectangular region, it is shown that, for any combination of problem parameters, there are only two candidate points in the region for the optimum location of the facility. This is also shown to be true for any convex and symmetric planar region. For the minimax problem in a rectangular region, there are only three candidate points for the optimal location. Some extensions and conjectures for the minisum problem involving more than one highway are also discussed.     

The power of quality models: The example of the SIQ model for performance excellence

Most contemporary total quality management (TQM) practice is influenced, directly or indirectly, by structured, acontextual and standardized quality models. The present paper focuses on the strategic introduction of one such model, namely the Swedish Institute for Quality (SIQ) model for performance excellence, in a Swedish public-sector organization, which we refer to as ‘the Authority.’ We take our theoretical stance from Foucault's concept of ‘power/knowledge.’ In describing the case, we focus on the management team of one of the Authority's ten regions. Our analysis shows the members of the management team using the SIQ model to objectify both the organization and themselves as managers. However, contrary to many critical or managerial accounts, the SIQ model was not totalizing: management subjectivities changed but were not entirely reconstituted, and some resistance to them was generated by the members of the management team, in their role as professionals.     

Economic dynamics of reservoir sedimentation management: Optimal control with singularly perturbed equations of motion

We analyze the economic dynamics of reservoir sedimentation management using the hydrosuction-dredging sediment-removal system. System dynamics depend on two interdependent hydraulic processes evolving at different rates. The accumulation of water impounded in the reservoir evolves on a ‘fast’ time scale, while the loss of water storage capacity to trapped sediments evolves on a ‘slow’ time scale. We formulate a multidimensional optimal control problem with singularly perturbed equations of motion to accommodate the disparate time scales. We apply singular perturbation methods to approximate (via polynomial series expansion) a ‘slow’ manifold reducing multi-dimensional solution space to the single-dimensional subspace confining long-term dynamics.     

Delivering the ‘3-day car’—the strategic implications for automotive logistics operations

It is now becoming apparent that the current ‘stock-push’ vehicle supply in the automotive industry by fulfilling the large majority of orders from existing stock is no longer a viable proposition. Cost pressure from rising stock levels in the market and high discounts needed to sell these vehicles have forced vehicle manufacturers to rethink their order fulfilment strategy in favour of stock-less ‘build-to-order’ systems. More responsive order fulfilment at vehicle manufacturer level however will not only require flexible and responsive component supply and vehicle assembly, but will also have wide ramifications for all logistics operations in the auto supply chain. Based on findings of the 3DayCar research programme, this paper compares the implications on inbound, outbound and sea transportation logistics, leading to the development of a strategic framework for future automotive logistics operations.     

The Delphi technique as a forecasting tool: issues and analysis

This paper systematically reviews empirical studies looking at the effectiveness of the Delphi technique, and provides a critique of this research. Findings suggest that Delphi groups outperform statistical groups (by 12 studies to two with two ‘ties’) and standard interacting groups (by five studies to one with two ‘ties’), although there is no consistent evidence that the technique outperforms other structured group procedures. However, important differences exist between the typical laboratory version of the technique and the original concept of Delphi, which make generalisations about ‘Delphi’ per se difficult. These differences derive from a lack of control of important group, task, and technique characteristics (such as the relative level of panellist expertise and the nature of feedback used). Indeed, there are theoretical and empirical reasons to believe that a Delphi conducted according to ‘ideal’ specifications might perform better than the standard laboratory interpretations. It is concluded that a different focus of research is required to answer questions on Delphi effectiveness, focusing on an analysis of the process of judgment change within nominal groups.     

A Hotelling model with a ceiling on the stock of pollution

Environmental agreements such as the Kyoto Protocol aim to stabilize the amount of carbon in the atmosphere, which is mainly caused by the burning of nonrenewable resources such as coal. We characterize the solution to the textbook Hotelling model when there is a ceiling on the stock of emissions. We consider both increasing and decreasing demand for energy. We show that when the ceiling is binding, both the low-cost nonrenewable resource and the high-cost renewable resource may be used jointly. A key implication is that if energy demand were to decline in the long run, we may supplement energy supply through ‘clean’ renewables to meet the environmental standard, but then revert back to using only ‘dirty’ fossil fuels in the future when the ceiling has become non-binding. That is, the much heralded societal ‘transition’ to clean energy resources may be short-lived.     

The spatial structure of production with a leontief technology – II: Substitute techniques

The structure of the optimal spatial pattern of production is studied when there are dependencies among production units which can be described by a Leontief technology with substitute techniques, and when there is a single marketplace of final demand, the CBD. Transportation cost is proportional to distance. The various goods are produced in rings. There are a finite number of patterns in which these rings are arranged, and they can be obtained by a finite algorithm. The particular pattern depends on the final demand. Hence there is no ‘non- substitution’ theorem. ‘Reswitching’ of techniques can occur, that is, in an optimal pattern a technique may be operated at large and small distances from the CBD, but not at intermediate distances; this contradicts prevailing beliefs about optimal capital/land profiles.     

Self-organized criticality in evolutionary systems with local interaction

This paper studies a stylized model of local interaction where agents choose from an ever increasing set of vertically ranked actions, e.g. technologies. The driving forces of the model are infrequent upward shifts (‘updates’), followed by a rapid process of local imitation (‘diffusion’). Our main focus is on the regularities displayed by the long-run distribution of diffusion waves and their implication on the performance of the system. By integrating analytical techniques and numerical simulations, we come to the following two main conclusions. (1) If non-coordination costs are sufficiently high, the system behaves critically, in the sense customarily used in physics. (2) The performance of the system is optimal at the frontier of the critical region. Heuristically, this may be interpreted as an indication that (performance-sensitive) evolutionary forces induce the system to be placed ‘at the edge of order and chaos’.