MODELS OF CONTINUITY

Summary. Recent discussions of continuity between Roman and Saxon Britain have not considered in detail the bases of dating, or the model which is being used to explain the transition from one state to the other. This builds considerable dangers and uncertainties into any future work. The problems inherent in late Roman and Early Saxon chronology are aired, the two most obvious current models of transition are considered, rejected, and replaced by a model involving minimal population movement but total change in fashions.     

HOMO ECONOMICUS, PHYSICAL METAPHORS, and UNIVERSAL MODELS IN ECONOMIC GEOGRAPHY

This paper argues that economic geography's assumption of economic rationality is misleading on two grounds: first, it applies an inappropriate physical metaphor to the human world; second, it is a universal model: it assumes an invariable relationship between the model and the thing modelled. In contrast, it is argued here that a more useful approach to studying spatial economic behaviour and the geographer's models of it is to begin with the local context in which each is embedded . Two types of local models are discussed: of investigatees and of modellers .
Le rationalisme économique qui est à la base de la géographic économique mène à des erreurs pour deux raisons: en premier lieu il constitue un exemple d'application à l'humain d'une métaphore physique impropre; en second lieu il est l'exemple d'un modèle universel - un modèle qui implique un rapport invariable entre le modèle lui-même et ce à quoi on l'applique. L'auteur cherche à prouver, qu'au contraire il est plus utile d'aborder l'étude des comportements spatioéconomiques, de même que celle des modèles appliqués par le géographe à ces comportements, en commençant par les lieux dans lesquels les uns et les autres sont enchassés. Deux types de ce qu'on appelle 'modèles locaux' sont abordés: le 'modèle local' des sujets de l'investigation, et celui du spécialiste qui applique le 'modèle local.'     

SPATIAL HEDONIC MODELS OF AIRPORT NOISE,PROXIMITY, AND HOUSING PRICES*

ABSTRACT Despite the refrain that housing prices are determined by “location, location, and location,” few studies of airport noise and housing prices have incorporated spatial econometric techniques. We compare various spatial econometric models and estimation methods in a hedonic price framework to examine the impact of noise on 2003 housing prices near the Atlanta airport. Spatial effects are best captured by a model including both spatial autocorrelation and autoregressive parameters estimated by a generalized moments approach. In our preferred model, houses located in an area in which noise disrupts normal activities (defined by a day–night sound level of 70–75 decibels) sell for 20.8 percent less than houses located where noise does not disrupt normal activities (defined by a day–night sound level below 65 decibels). The inclusion of spatial effects magnifies the negative price impacts of airport noise. Finally, after controlling for noise, houses farther from the airport sell for less; the price elasticity with respect to distance is −0.15, implying that airport proximity is an amenity.     

OPTIMAL REGIONAL GROWTH MODELS: MULTIPLE OBJECTIVES, SINGULAR CONTROLS, AND SUFFICIENCY CONDITIONS

ABSTRACT We develop a generalized Harrod-Domar type of model for optimal regional growth which allows determination of the optimal allocation of regional public investments and which considers multiple growth objectives, as well as both normal and singular fiscal instruments. This general model is shown to include most of the previous optimal regional growth models as special cases. Necessary conditions for some special cases of the general model are analyzed in detail, and decision rules associated with derived optimal regional growth policies are articulated. These special cases verify that singular controls do exist in certain instances, and that they must be considered for the complete specification of optimal regional growth policies; this is significant because singular controls have not been previously analyzed in the literature. We conclude the paper with a discussion of sufficiency conditions for optimal regional growth models which is more general than that given by previous authors.     

SUPPLY-SIDE MULTIREGIONAL INPUT-OUTPUT MODELS*

ABSTRACT This paper introduces a new class of supply-side multiregional input-output (MRIO) models and provides the necessary and sufficient conditions on the regional trade matrices that ensure that a generalized supply-side model will be convergent. The paper also introduces a new version of the row coefficient model, conceived as the “mirror image” of the Chenery-Moses demand-side column coefficient MRIO model. Given that the conventional supply-side input-output model has been shown to perform equally as well as the demand side model in forecasting exercises, the supply-side MRIO model is expected to be of value for policy and planning purposes. Moreover, this model is of potential theoretical value for a broad synthesis of demand-side and supply-side MRIO models.     

ADDITIVE-INTERACTION MODELS OF SPATIAL AGGLOMERATION*

A wide variety of existing models of spatial agglomeration postulate additive-interaction effects among agents. In this paper, a synthesis of such models is achieved by establishing certain mathematical equivalences between them. In particular, it is shown that Rockafellar's conjugacy theory of concave functions yields a symmetric one-to-one correspondence between three classes of existing models, here designated as spatial-accessibility models, endogenous-contact models, and fixed-contact models. These correspondences not only allow the transference of results between models, but also suggest new economic interpretations of each model in terms of its conjugate model. A series of examples are drawn from the literature to illustrate these results.     

ELASTICITIES OF CONSTRAINED GRAVITY MODELS*

ABSTRACT Doubly constrained gravity models require a balancing procedure to make estimated origin and destination totals consistent. We show through a series of examples that not just the magnitudes but even the signs of derivatives and elasticities of gravity model flows depend on the specific balancing procedure used. Hence, if such elasticities are regarded as meaningful, then the balancing of origin and destination totals must be regarded as an integral part of the gravity theory itself.