A generalised nested-logit model of the demand for automobile variants

This paper estimates the demand for car model variants instead of looking only at demand for models in terms of the ’baseline’ variant of each model as done in the literature. The data has sex and age of the buyer for every car sold in Norway 2000-2004, in addition to characteristics of the cars. The demand model uses this information to estimate taste coefficients which depend on demographic characteristics. A nested logit model and a generalised nested logit model are used to induce correlation in the logit error between products with observable and unobservable similarities. Results indicate that it may be problematic to have different logit errors for every product when the number of products is very high, even when allowing for flexible correlation patterns.

Bounds on willingness-to-pay in a pure-characteristics model of the demand for automobile variants

I estimate a pure-characteristics discrete choice model of the demand for automobile engine and body style variants, using market-level data. Revealed preference bounds and imposed bounds on the willingness to pay for characteristics as a percentage of product price are sufficient to identify nonparametric taste distributions. Substitution patterns as determined by closest substitutes appear very realistic. The model can be estimated on a single cross-section of data.

Automobile engine variants and price discrimination

Using a structural model of demand for automobile engine variants, this paper finds that there is second-degree price discrimination: markups increase with engine size. Still, average markups are lower than when models have just one engine. The paper develops the first empirical demand framework suitable for markets with variants. There is an unobserved product characteristic and a consumer-specific logit term for classes of products, but both are fixed across variants. Fixed effects control for unobservables. The literature’s assumption of orthogonality between unobserved and observed product characteristics is not needed.second-degree price discrimination, automobiles, discrete-choice demand models

A Generalised Nested-Logit Model of the Demand for Automobile Variants

This paper estimates the demand for car model variants instead of looking only at demand for models in terms of the baseline variant of each model as done in the literature. The data has sex and age of the buyer for every car sold in Norway 2000-2004, in addition to characteristics of the cars. The demand model uses this information to estimate taste coefficients which depend on demographic characteristics. A nested logit model and a generalised nested logit model are used to induce correlation in the logit error between products with observable and unobservable similarities. Results indicate that it may be problematic to have different logit errors for every product when the number of products is very high, even when allowing for flexible correlation patterns

A two sample size estimator for large data sets

In GMM estimators moment conditions with additive error terms involve an observed component and a predicted component. If the predicted component is computationally costly to evaluate, it may not be feasible to estimate the model with all the available data. We propose an estimator that uses the full data set for the computationally cheap observed component, but a reduced sample size for the predicted component. We show consistency, asymptotic normality, and derive standard errors and a practical criterion for when our estimator is variance-reducing. We demonstrate the estimator’s properties on a range of models through Monte Carlo studies and an empirical application to alcohol demand

Multi-category competition and market power: a model of supermarket pricing

In many competitive settings consumers buy multiple product categories, and some prefer to use a single firm, generating complementary cross-category price effects. To study pricing in supermarkets, an organizational form where these effects are internalized, we develop a multi-category multi-seller demand model and estimate it using UK consumer data. This class of model is used widely in theoretical analysis of retail pricing. We quantify crosscategory pricing effects and find that internalizing them substantially reduces market power. We find that consumers inclined to one-stop (rather than multi-stop) shopping have a greater pro-competitive impact because they generate relatively large cross-category effect

Comparison of three different prehospital wrapping methods for preventing hypothermia - a crossover study in humans

<p>Abstract</p> <p>Background</p> <p>Accidental hypothermia increases mortality and morbidity in trauma patients. Various methods for insulating and wrapping hypothermic patients are used worldwide. The aim of this study was to compare the thermal insulating effects and comfort of bubble wrap, ambulance blankets / quilts, and Hibler's method, a low-cost method combining a plastic outer layer with an insulating layer.</p> <p>Methods</p> <p>Eight volunteers were dressed in moistened clothing, exposed to a cold and windy environment then wrapped using one of the three different insulation methods in random order on three different days. They were rested quietly on their back for 60 minutes in a cold climatic chamber. Skin temperature, rectal temperature, oxygen consumption were measured, and metabolic heat production was calculated. A questionnaire was used for a subjective evaluation of comfort, thermal sensation, and shivering.</p> <p>Results</p> <p>Skin temperature was significantly higher 15 minutes after wrapping using Hibler's method compared with wrapping with ambulance blankets / quilts or bubble wrap. There were no differences in core temperature between the three insulating methods. The subjects reported more shivering, they felt colder, were more uncomfortable, and had an increased heat production when using bubble wrap compared with the other two methods. Hibler's method was the volunteers preferred method for preventing hypothermia. Bubble wrap was the least effective insulating method, and seemed to require significantly higher heat production to compensate for increased heat loss.</p> <p>Conclusions</p> <p>This study demonstrated that a combination of vapour tight layer and an additional dry insulating layer (Hibler's method) is the most efficient wrapping method to prevent heat loss, as shown by increased skin temperatures, lower metabolic rate and better thermal comfort. This should then be the method of choice when wrapping a wet patient at risk of developing hypothermia in prehospital environments.</p

Implementation of checklists in health care; learning from high-reliability organisations

<p>Abstract</p> <p>Background</p> <p>Checklists are common in some medical fields, including surgery, intensive care and emergency medicine. They can be an effective tool to improve care processes and reduce mortality and morbidity. Despite the seemingly rapid acceptance and dissemination of the checklist, there are few studies describing the actual process of developing and implementing such tools in health care. The aim of this study is to explore the experiences from checklist development and implementation in a group of non-medical, high reliability organisations (HROs).</p> <p>Method</p> <p>A qualitative study based on key informant interviews and field visits followed by a Delphi approach. Eight informants, each with 10-30 years of checklist experience, were recruited from six different HROs.</p> <p>Results</p> <p>The interviews generated 84 assertions and recommendations for checklist implementation. To achieve checklist acceptance and compliance, there must be a predefined need for which a checklist is considered a well suited solution. The end-users ("sharp-end") are the key stakeholders throughout the development and implementation process. Proximity and ownership must be assured through a thorough and wise process. All informants underlined the importance of short, self-developed, and operationally-suited checklists. Simulation is a valuable and widely used method for training, revision, and validation.</p> <p>Conclusion</p> <p>Checklists have been a cornerstone of safety management in HROs for nearly a century, and are becoming increasingly popular in medicine. Acceptance and compliance are crucial for checklist implementation in health care. Experiences from HROs may provide valuable input to checklist implementation in healthcare.</p

Wind and Fisheries: Desktop Study on the Coexistence Between Offshore Wind and Fisheries in Sothern North Sea II

The Norwegian Government has launched a major initiative to promote offshore wind power , in which bottom-fixed wind power will be developed in the Southern North Sea II (SN II) area. There is a low level of fishing activities in this area with varying catch sizes over the years. The activities consist nearly exclusively of bottom trawling of sandeel. The fishing industry has raised concerns about the development of offshore wind farms (OWFs), including risks for collision and hindrance for fishing vessels, negative impacts on fish stocks, and other ecosystem-wide effects. This report has conducted a data study and compiled existing literature on these topics to, based on best available science, assess how OWF development could affect fisheries in SN II, the possibilities for facilitating coexistence for these two industries, and potential synergies. While the development of OWFs in SN II has the potential to bring both positive and negative effects on the fisheries as well as the marine life in the area, the findings suggest that coexistence between the two industries is possible. Potential impacts, including noise, magnetic fields, turbidity, artificial reef and FAD effects, and no-fishing zones, have not been shown to adversely affect populations of commercially important fish at OWF developments in the North Sea. With the ongoing technology shift to larger turbines, the space between each turbine is increasing, which may reduce collision risk. Seafloor cables can also be sufficiently buried to reduce the risk of damage by demersal trawls. Furthermore, most types of passive fishing gear (except for drifting nets) and practices are less problematic to use in an OWF. Should, though, the construction of OWFs in SN II cause restrictions on the fishery activities in the area, it is likely to cause increased fishing in other areas, often referred to in the scientific literature as the displacement effect, indicating that the economic loss will be smaller than the estimated catch values. Notable knowledge gaps are regarding positive and negative long term cumulative impacts and regional effects, impact on primary production and carbon assimilation from changed upper ocean mixing and impact from floating wind farms (not relevant in SN II). We emphasise the importance of early and ongoing input from relevant stakeholders to address concerns and find optimal mitigation measures for minimising the OWF footprint in SN II during the different phases of OWF development.Wind and Fisheries: Desktop Study on the Coexistence Between Offshore Wind and Fisheries in Sothern North Sea IIpublishedVersio

Prevalence and Self-Perceived Experiences With the Use of Hormonal Contraceptives Among Competitive Female Cross-Country Skiers and Biathletes in Norway: The FENDURA Project

Purpose: To investigate the prevalence of hormonal contraceptive (HC) use by female cross-country (XC) skiers and biathletes competing at a national and/or international level, their reasons for HC use, and to compare negative symptoms related to the HC-/menstrual cycle in HC users and non-HC users. Additionally, to characterize the self-perceived influence of HC use on training and performance. Methods: A total of 113 Norwegian competitive XC skiers and biathletes completed an online questionnaire including both closed and open-ended questions. The questions were designed to assess the type of HC, reasons for use, self-reported negative symptoms related to HC-/menstrual cycle, as well as athletes' experiences regarding how HC use affects training and performance. Results: In total, 68% of all the athletes used HC, with 64 and 36% of them using a progestin-only and combined type HC, respectively. Non-contraceptive reasons for HC use were reported by 51% of the progestin-only HC users vs. 75% of the combined HC users (P = 0.039), with reduction of negative menstrual-related symptoms as the most common reason. Of the athletes reporting regular withdrawal bleedings in connection to HC use, 80% of the progestin-only and 86% of combined HC users experienced negative menstrual-related symptoms, which was comparable to the non-HC group (86%). The majority (81%) of HC users experienced solely positive, or no effect, of HC use on training and performance, with no differences between progestin-only and combined HC users (P = 0.942). Conclusions: In total, 68% of the XC skiers and biathletes used HC, with the highest proportion (64%) using a progestin-only HC. Many athletes used HC to manipulate their menstrual cycle due to perceived negative menstrual-related symptoms that interfered with their training sessions and/or competitions