Estimating Variable Returns to Scale Production Frontiers with Alternative Stochastic Assumptions

A stochastic production frontier model is formulated within the generalized production function framework popularized by Zellner and Revankar (1969) and Zellner and Ryu (1998). This framework is convenient for parsimonious modeling of a production function with variable returns to scale specified as a function of output. Two alternatives for introducing the stochastic inefficiency term and the stochastic error are considered, one where they are appended to the existing equation for the production relationship and one where the existing equation is solved for the log of output before the stochastic terms are added. The latter alternative is novel, but it is needed to preserve the usual definition of firm efficiency. The two alternative stochastic assumptions are considered in conjunction with two returns to scale functions, making a total of four models that are considered. A Bayesian framework for estimating all four models is described. The techniques are applied to USDA state-level data on agricultural output and four inputs. Posterior distributions for all parameters, firm efficiencies and the efficiency rankings of firms are obtained. The sensitivity of the results to the returns to scale specification and to the stochastic specification is examined.

PREDICTING OUTPUT FROM SEEMINGLY UNRELATED AREA AND YIELD EQUATIONS

Crop output can be defined as the product of area sown and yield. Given the existence of separate equations for explaining and predicting area sown and yield, in this paper we suggest predictors for output and derive expressions for the standard errors of the predictors. The methodology is applied to wheat production in the Corrigin Shire of Western Australia.Predicting a product, standard error of prediction, Crop Production/Industries,

IMPOSING REGULARITY CONDITIONS ON A SYSTEM OF COST AND FACTOR SHARE EQUATIONS

Systems of equations comprising cost functions and first-order derivative equations are often used to estimate characteristics of production technologies. Unfortunately, many estimated systems violate the regularity conditions implied by economic theory. Sampling theory methods can be used to impose these conditions globally, but these methods destroy the flexibility properties of most functional forms. We demonstrate how Bayesian methods can be used to maintain flexibility by imposing regularity conditions locally. The Bayesian approach is used to estimate a system of cost and share equations for the merino-woolgrowing sector. The effect of local imposition of monotonicity and concavity on the signs and magnitudes of elasticities is examined.Cost functions, Markov Chain Monte Carlo, inequality constraints, Demand and Price Analysis,

Imposing regularity conditions on a system of cost and factor share equations

Systems of equations comprising cost functions and first‐order derivative equations are often used to estimate characteristics of production technologies. Unfortunately, many estimated systems violate the regularity conditions implied by economic theory. Sampling theory methods can be used to impose these conditions globally, but these methods destroy the flexibility properties of most functional forms. We demonstrate how Bayesian methods can be used to maintain flexibility by imposing regularity conditions locally. The Bayesian approach is used to estimate a system of cost and share equations for the merino wool‐growing sector. The effect of local imposition of monotonicity and concavity on the signs and magnitudes of elasticities is examined.Resource /Energy Economics and Policy,

Electromagnetics from a quasistatic perspective

Quasistatics is introduced so that it fits smoothly into the standard textbook presentation of electrodynamics. The usual path from statics to general electrodynamics is rather short and surprisingly simple. A closer look reveals however that it is not without confusing issues as has been illustrated by many contributions to this Journal. Quasistatic theory is conceptually useful by providing an intermediate level in between statics and the full set of Maxwell's equations. Quasistatics is easier than general electrodynamics and in some ways more similar to statics. It is however, in terms of interesting physics and important applications, far richer than statics. Quasistatics is much used in electromagnetic modeling, an activity that today is possible on a PC and which also has great pedagogical potential. The use of electromagnetic simulations in teaching gives additional support for the importance of quasistatics. This activity may also motivate some change of focus in the presentation of basic electrodynamics

Electrostatic internal energy using the method of images

For several configurations of charges in the presence of conductors, the method of images permits us to obtain some observables associated with such a configuration by replacing the conductors with some image charges. However, simple inspection shows that the potential energy associated with both systems does not coincide. Nevertheless, it can be shown that for a system of a grounded or neutral conductor and a distribution of charges outside, the external potential energy associated with the real charge distribution embedded in the field generated by the set of image charges is twice the value of the internal potential energy associated with the original system. This assertion is valid for any size and shape of the conductor, and regardless of the configuration of images required. In addition, even in the case in which the conductor is not grounded nor neutral, it is still possible to calculate the internal potential energy of the original configuration through the method of images. These results show that the method of images could also be useful for calculations of the internal potential energy of the original system.Comment: 5 pages, 3 figures. New discussions added. Minor change

Abundance of Selected Fish Species in Relation to Temperature and Salinity Patterns in the Sagavanirktok Delta, Alaska, Following Construction of the Endicott Causeway

Hydrography data from 1985 to 1993 in the vicinity of the Endicott Causeway near Prudhoe Bay, Alaska, were analyzed to determine if the trend in yearly post-causeway construction temperature and salinity was toward colder and more saline conditions. No significant (P<=0.05) relationship was found for temperature; however, salinity levels significantly decreased with time following construction. Intra-year variations in hydrographic conditions appeared to be due to coast-wide meteorological and oceanographic events rather than causeway-induced. We analyzed abundance indices, as log e, transformed catch-per-unit-effort (CPUE), of four marine species (arctic cod, Boreogadus saida; fourhorn sculpin, Myoxocephalus quadricornis; arctic flounder, Pleuronectes glacialis; saffron cod, Eleginus gracilis); two freshwater species (round whitefish, Prosopium cylindraceum; arctic grayling, Thymallus arcticus); and the anadromous rainbow smelt, Osmerus mordax, to determine whether there were increases in the abundance of marine species and declines in anadromous and freshwater species. We developed the "best-fit" regression models, based on the criterion of maximized regression F-ratio (i.e., minimized regression p-values), using year, temperature, salinity, and all possible interactions. Results suggested that all species exhibited changes in abundance levels over the period of record. In particular, arctic flounder and rainbow smelt both showed sharp increases in abundance five years after construction. For all species, the observed changes in abundance levels appears to be due to naturally occurring events in the species life history or changes in coast-wide meteorological conditions rather than to causeway-induced alterations in local hydrographic conditions.On a analysé les données hydrographiques obtenues de 1985 à 1993 dans le voisinage immédiat du pont-jetée Endicott situé près de Prudhoe Bay en Alaska, en vue de déterminer si, après la construction du pont, la température annuelle avait tendance à être plus froide et l'eau plus saline. On n'a trouvé aucun rapport significatif (p <= 0,05) pour la température. Le niveau de salinité, par contre, a considérablement baissé à mesure que le temps passait après la construction. Les variations intra-annuelles dans les conditions hydrographiques semblaient être dues à des phénomènes météorologiques et océanographiques affectant le littoral tout entier plutôt qu'au pont-jetée lui-même. On a analysé les indices d'abondance, exprimés en log\dn4 e des prises par unité d'effort (PPUE) de quatre espèces marines (morue arctique, Boreogadus saida; chaboisseau à quatre cornes, Myoxocephalus quadricornis; plie arctique, Pleuronectes glacialis; navaga jaune, Eleginus gracilis); deux espèces d'eau douce (ménomini rond, Prosopium cylindraceum, et ombre arctique, Thymallus arcticus); ainsi qu'une espèce anadrome (éperlan arc-en-ciel, Osmerus mordax), afin de déterminer s'il y avait une augmentation dans l'abondance des espèces marines et une diminution dans les espèces anadromes et d'eau douce. On a développé des modèles de régression de meilleur ajustement, fondés sur le critère de maximisation du F de régression (c.-à-d. minimum des valeurs p de régression), en utilisant l'année, la température, la salinité et toutes les interactions possibles. Les résultats suggéraient que toutes les espèces montraient des changements dans les niveaux d'abondance durant la période de relevés. La plie arctique et l'éperlan arc-en-ciel en particulier affichaient tous deux un accroissement très net dans leur abondance cinq ans après la construction. Pour toutes les espèces, les changements observés dans les niveaux d'abondance semblent être dûs à des phénomènes qui se produisent naturellement dans le cycle biologique de l'espèce ou à des changements dans les conditions météorologiques affectant le littoral tout entier plutôt qu'à des transformations causées par le pont-jetée dans les conditions hydrographiques locales

Sterolomics: State of the Art, Developments, Limitations and Challenges

Sterolomics can be thought of as the quantitative determination of the entire complement of molecules based on the cyclopentanoperhydrophenanthrene skeleton in a system. Mass spectrometry is the dominant analytical technology employed. In this article we highlight some pitfalls in analysis, data interpretation and annotation. We give our opinion on how some of these pitfalls can best be avoided

Prudhoe Bay Causeways and the Summer Coastal Movements of Arctic Cisco and Least Cisco

Catch-per-unit-effort and mark-recapture data collected by fyke net during the summers of 1985-93 near Prudhoe Bay, Alaska, were analyzed to determine whether two oil industry causeways constructed perpendicular to the Beaufort Sea coast, West Dock and the Endicott Causeway, affected the feeding and migratory patterns of least cisco (Coregonus sardinella) and arctic cisco (C. autumnalis). During two of the four years in which juvenile least cisco were abundant in the study area, catch rates were significantly lower (P<=0.0005) east of West Dock, which suggested that small fish traveling eastward along the coast failed to bypass the causeway. Hydrographic conditions were generally consistent with the hypothesis that causeway-induced upwellings of saline marine water immediately west of West Dock may affect alongshore movement. No such disparities in catch were observed at the Endicott Causeway. We studied rates of return for subadult and adult (>=250 mm) arctic cisco and least cisco tagged in the Prudhoe Bay area and recovered in a commercial fishery that operates in the Colville River, Alaska. The expected rate of return was compared with actual rates of return over five years (for least cisco) and six years (for arctic cisco). Rates of return were based upon three areas of release: east of the easternmost causeway, west of the westmost causeway, and between the two causeways. For both species, across the regions and all year, there was no significant difference (p=0.25 for least cisco; p=0.30 for arctic cisco) between the expected and actual rates of tag returns. The contrasting effects of the two causeways are discussed in terms of their design and location.Les données de prises par unité d'effort et de marquage-recapture, recueillies par des verveux au cours des étés de 1985 à 1993 près de Prudhoe Bay en Alaska, ont été analysées afin de déterminer si deux ponts-jetées construits pour l'industrie pétrolière perpendiculairement au rivage de la mer de Beaufort (le pont-jetée West Dock et le pont-jetée Endicott) affectaient les schémas de nutrition et de migration du cisco sardinelle (Coregonus sardinella) et du cisco arctique (C. autumnalis). Durant deux des quatre années au cours desquelles le cisco sardinelle juvénile était abondant dans la zone de l'étude, les taux de prises étaient sensiblement inférieurs (p <= 0,0005) à l'est du West Dock, ce qui suggérait que les poissons de petite taille se dirigeant vers l'est le long de la côte ne réussissaient pas à contourner le pont-jetée. En général, les conditions hydrographiques concordaient avec l'hypothèse que les remontées d'eau marine salée provoquées par le pont-jetée juste à l'ouest du West Dock peuvent affecter le mouvement le long du rivage. On n'a observé aucun écart de ce genre dans les prises au pont-jetée Endicott. On a étudié les taux de retour pour les jeunes adultes et les adultes (>= 250 mm) du cisco arctique et du cisco sardinelle, marqués dans la région de la baie de Prudhoe et recapturés dans une pêcherie commerciale en exploitation sur la rivière Colville en Alaska. On a comparé le taux de retour escompté aux taux de retour réels sur cinq ans (pour le cisco sardinelle) et sur six ans (pour le cisco arctique). Les taux de retour s'appuyaient sur trois zones de remise à l'eau: à l'est du pont-jetée le plus oriental, à l'ouest du plus occidental et entre les deux. En tenant compte des trois emplacements et de toutes les années, il n'y avait pas de différence marquante pour les deux espèces (p = 0,25 pour le cisco sardinelle; p = 0,30 pour le cisco arctique) entre les taux de retour prévus et les taux réels des individus marqués. On discute les effets opposés des deux ponts-jetées en considérant leur design et leur emplacement

Estimating the Hydrographic Effects of Prudhoe Bay Causeway Breaches Using the Before-After Control-Impact (BACI) Analysis

A Before-After Control-Impact (BACI) analysis was used to test the effects of new breaches constructed in two Prudhoe Bay causeways on hydrographic conditions during the open-water summer season. At West Dock, under east wind conditions, significant cross-causeway differentials in salinity and temperature at the surface (1 m depth or less) were observed in all eight pre-breach cases tested. In the years following construction of the breach, there were no significant cross-causeway differentials in seven of those eight cases. At Endicott Causeway, under east wind conditions, significant cross-causeway differentials in surface salinity and temperature were observed in all eight pre-breach cases tested. Significant cross-causeway differentials continued in all eight cases following construction of the new breach. Results suggest that the new breach at West Dock has successfully mitigated cross-causeway hydrographic differentials, and that the new breach at the Endicott Causeway has had no observable effect. The possible reasons for this disparity include different hydrographic dynamics in the vicinity of each causeway.On a procédé à une analyse de contrôle-incidence avant-après pour tester les effets de nouvelles brèches aménagées dans deux ponts-jetées de la baie Prudhoe sur les conditions hydrographiques durant la saison estivale d'eau libre. Au West Dock, par vent d'est, on a observé des écarts notables de part et d'autre du pont-jetée dans la salinité et la température de surface (jusqu'à 1 m de profondeur) dans les huit tests effectués avant l'aménagement de la brèche. Au cours des années suivantes, on n'a relevé aucun écart notable de part et d'autre du pont-jetée dans sept de ces huit cas. Au pont-jetée Endicott, par vent d'est, on a relevé d'importants écarts dans la salinité et la température de surface dans les huit tests datant d'avant la brèche. D'importants écarts de part et d'autre ont continué à se manifester dans les huit cas, après la construction de la nouvelle brèche. Les résultats suggèrent qu'au West Dock, la nouvelle brèche a réussi à atténuer les écarts hydrographiques, et qu'au pont-jetée Endicott, elle n'a pas causé d'effet observable. Parmi les raisons possibles de cette disparité, il faut compter une différence dans la dynamique hydrographique au voisinage de chaque pont-jetée