Least squares model averaging by Mallows criterion

This paper is in response to a recent paper by Hansen (2007) who proposed an optimal model average estimator with weights selected by minimizing a Mallows criterion. The main contribution of Hansen’s paper is a demonstration that the Mallows criterion is asymptotically equivalent to the squared error, so the model average estimator that minimizes the Mallows criterion also minimizes the squared error in large samples. We are concerned with two assumptions that accompany Hansen’s approach. The first is the assumption that the approximating models are strictly nested in a way that depends on the ordering of regressors. Often there is no clear basis for the ordering and the approach does not permit non-nested models which are more realistic from a practical viewpoint. Second, for the optimality result to hold the model weights are required to lie within a special discrete set. In fact, Hansen noted both difficulties and called for extensions of the proof techniques. We provide an alternative proof which shows that the result on the optimality of the Mallows criterion in fact holds for continuous model weights and under a non-nested set-up that allows any linear combination of regressors in the approximating models that make up the model average estimator. These results provide a stronger theoretical basis for the use of the Mallows criterion in model averaging by strengthening existing findings.     

Modelling the Risks Associated with the Increased Importation of Fresh Produce from Emerging Supply Sources Outside the EU to the UK

The risk of non‐indigenous plant pests entering the UK via international trade in fresh produce is increasing. The objective of this article is to identify existing and emerging supply sources for UK fresh produce importers and examine the extent to which they could provide invasion pathways. We tested the hypothesis that increased imports of fresh produce from new sources outside the European Union could increase the risks of non‐indigenous insect pests. We use a bio‐economic model approach in which the number of species arrivals is a function of the volume of imports, whereas the volume of imports itself is a function of gross domestic product, relative import prices and seasonality. The study has identified clear trends, which show import volumes of fresh produce and species detections increasing from new supply sources. If this trend continues in the future, then the UK inspection agency should expect to confront species from new suppliers in much greater numbers, given that import volumes of fresh produce are income elastic.     

Parental preferences and choice of school

This paper provides a UK high resolution microeconometric study of parental preferences and the choice process for secondary schools. Given the particular geographical features of the region, first preference almost entirely related to one of two state schools, which is a situation that perhaps better reflects the real nature of the options faced by most parents in the UK. In contrast to earlier work, distance and access considerations were explicitly incorporated in the preference and choice models estimated and found to be a significant influence on parental decisions. Further significant factors were found, dependent upon the parents' actual choice of school.     

The cell phone effect on motor vehicle fatality rates: A Bayesian and classical econometric evaluation

This paper examines the potential effect of cell phones on motor vehicle fatality rates normalized for other driving related and socioeconomic factors. The model used is non-linear so as to address both life-taking and life-saving attributes of cell phones. The model is evaluated using classical methods along with Bayesian Extreme Bounds Analysis (EBA). The use of both classical and Bayesian methods diminishes the model and parameter uncertainties which afflict more conventional modeling methods which rely on only one of the two methods. The results indicate the presence of both life-taking and life-saving attributes of cell phones on motor vehicle fatality rates depending on the volume of cell phone subscribers in existence.     

Factors associated with single-vehicle and multi-vehicle road traffic collision injuries in Ireland

Generalised linear regression models were used to identify factors associated with fatal/serious road traffic collision injuries for single- and multi-vehicle collisions. Single-vehicle collisions and multi-vehicle collisions occurring during the hours of darkness or on a wet road surface had reduced likelihood of a fatal/serious injury. Single-vehicle ‘driver with passengers’ collisions occurring at junctions or on a hill/gradient were less likely to result in a fatal/serious injury. Multi-vehicle rear-end/angle collisions had reduced likelihood of a fatal/serious injury. Single-vehicle ‘driver only’ collisions and multi-vehicle collisions occurring on a public/bank holiday or on a hill/gradient were more likely to result in a fatal/serious injury. Single-vehicle collisions involving male drivers had increased likelihood of a fatal/serious injury and single-vehicle ‘driver with passengers’ collisions involving drivers under the age of 25 years also had increased likelihood of a fatal/serious injury. Findings can enlighten decision-makers to circumstances leading to fatal/serious injuries.     

An investigation into the relationship between training evaluation and the transfer of training

The purpose of this study was to investigate the relationship between training evaluation and the transfer of training in organizations. We hypothesized that training evaluation frequency will be related to higher rates of transfer because evaluation information can identify weaknesses that lead to improvements in training programs and create greater accountability among stakeholders for training outcomes. The data were obtained from 150 training professionals who were members of a training and development association in Canada. The results indicated that training evaluation frequency is positively related to training transfer. However, among Kirkpatrick's four levels of evaluation criteria, only behavior and results criteria were related to higher rates of transfer of training, indicating that the level of evaluation criteria is important for training transfer. These results indicate the importance of organizational‐level initiatives such as training evaluation in addition to individual‐level practices for facilitating the transfer of training.     

Product development with multiple partners: Strategies and conflicts in networks

This paper provides an insight into and discusses the variety of sources of conflict in linking multiple partners in a network to the product development process. Conflict issues are discussed in relation to focal company strategies for product development within networks. On the basis of three case studies representing three different strategic intentions and network situations, our findings suggest that the sources of conflict are related to the actors' definition and negotiation of the development task at hand. The study suggests that the ability to combine and find complementarities in the strategic intentions of the multiple participating actors is essential to accomplish innovation. The paper concludes that influential actors initiating or acceding to changes are crucial for reaching a positive outcome in joint product development.     

START FILLING YOUR TALENT GAP-NOW

As businesses steer their way out of turbulence, they have a unique opportunity to identify their leadership supply and demand and then to close the talent gap in their organization. Alan Bird, Lori Flees and Paul DiPaola explain how you can take immediate steps to build the right team now – and lay the groundwork for a long-term approach for nurturing talent within the organization.     

Research needs for assessing online value creation in complex consumer purchase process behavior

Consumers face considerable frustration when purchasing structurally and/or semantically complex high-involvement products online. Reliance on computer-mediated communications for their information needs may result in functional and emotional frustration from information overload and lack of personal trust. This paper proposes a responsive real-time information system as a proxy for a perceptive sales representative who assesses customer needs based on information exchanges and then offers appropriate responses. By tracking and analyzing a consumer's online activity, vendors can offer information relevant to the consumer's real-time needs, facilitating their purchase process. In essence, this is a real-time value co-creation process based on the consumer offering cues to vendors through their key strokes and mouse click activity. This allows for differentiated information offerings for inexperienced and more experienced consumers, creating value by dynamic information serving. Where appropriate value is created, consumers will experience less frustration and continue online, rather than possibly moving offline or to alternative vendors. In examining the bases of consumer information needs in complex purchases, this paper identifies the data required to enable a responsive dialog between vendors and consumers.     

Firm Heterogeneity,New Investment and Acquisitions

This paper presents a model of investment in which heterogeneous firms choose between new investment and acquisitions. New investment involves purchasing a new plant for an existing variety. Acquisitions involve purchasing a plant and a variety from a selling firm. Using a variable‐elasticity demand system, I show that if varieties within a differentiated industry are imperfect substitutes, mid‐productivity firms invest. As varieties approach perfect substitutability, high‐productivity firms invest. For both cases, within the region of investing firms, the most productive choose acquisitions over new investment. In analyzing firm‐level data from Compustat, I find evidence that supports these predictions.