Bargaining power and supply base diversification

In this paper, the authors examine a supply base diversification problem faced by a buyer who periodically holds auctions to award short term supply contracts among a cohort of suppliers (i.e., the supply base). To mitigate significant cost shocks to procurement, the buyer can diversify her supply base by selecting suppliers from different regions. The authors find that the optimal degree of supply base diversification depends on the buyer’s bargaining power, i.e., the buyer’s ability to choose the auction mechanism. At one extreme, when the buyer has full bargaining power and thus can dictatorially implement the optimal mechanism, she prefers to fully diversify. At the other extreme, when the buyer uses a reverse English auction with no reserve price due to her lack of bargaining power, she may consider protecting herself against potential price escalation from cost-advantaged suppliers by using a less diversified supply base. The authors find that in general the more bargaining power the buyer has to control price escalation from cost-advantaged suppliers the more she prefers a diversified supply base. This insight is shown to be robust to correlation between regional costs, asymmetry across regions, and intermediate levels of bargaining power.supply base diversification; supplier; buyer; procurement; bargaining

Explaining Regional and Local Differences in Organic Farming in England and Wales: A Comparison of South West Wales and South East England

Explaining regional and local differences in organic farming in England and Wales: a comparison of South West Wales and South East England, Regional Studies, Few studies explain the concentration of organic farming in specific regions of England and Wales. This paper compares the development of organic farming in South West Wales and South East England. While the focus in the former is on the use of mainly national marketing channels and the movement of organic produce more than 60 min from the farm, in the latter greater use is made of local and direct marketing channels to distribute organic food within 30 min of the farm. The overriding importance of demand appears to provide a key explanation for regional differentiation in organic farming. 解释英格兰与威尔斯有机农业的区域及地方差异：西南威尔斯与东南英格兰的比较研究，区域研究。显少有研究解释有机农业在英格兰及威尔斯特定区域中的集中现象。本文比较有机农业在西南威尔斯与东南英格兰的发展。西南威尔斯的发展重点，主要在于利用全国行销通路，以及距离农场超过六十分钟的有机产品运送路程，东南英格兰则较着重运用在地且直接的行销通路，在距离农场三十分钟以内的运送路程中分派有机食品。需求的压倒性重要性，似乎提供了有机农业中的区域差异的关键解释。 Expliquer les disparités régionales dans l'agriculture biologique en Angleterre et au pays de Galles: une comparaison du sud-ouest du pays de Galles et du sud-est de l'Angleterre, Regional Studies. Rares sont les études qui expliquent la concentration de l'agriculture biologique dans des zones spécifiques de l'Angleterre et du pays de Galles. Cet article cherche à comparer le développement de l'agriculture biologique du sud-ouest du pays de Galles à celle du sud-est de l'Angleterre. Tandis que celle-là met l'accent sur l'emploi des circuits commerciaux principalement nationaux et sur la distribution de la production agricole biologique à plus de 60 minutes de la ferme, celle-ci exploite davantage les circuits commerciaux locaux et directs pour distribuer les denrées alimentaires organiques dans un rayon de 30 minutes de la ferme. Il semble que l'importance primordiale de la demande constitue un facteur déterminant de la différenciation régionale de l'agriculture biologique. Erklärung der regionalen und lokalen Unterschiede bei der ökologischen Landwirtschaft in England und Wales: ein Vergleich zwischen Südwestwales und Südostengland, Regional Studies. Die Konzentration der ökologischen Landwirtschaft in bestimmten Regionen von England und Wales wird nur in wenigen Studien erklärt. In diesem Beitrag vergleichen wir die Entwicklung der ökologischen Landwirtschaft in Südwestwales mit der von Südostengland. Während in Südwestwales der Schwerpunkt auf den größtenteils landesweiten Absatzkanälen und dem Transport von ökologischen Lebensmitteln an mehr als 60 Minuten vom landwirtschaftlichen Betrieb entfernte Orte liegt, werden in Südostengland öfter lokale und direkte Absatzkanäle genutzt und die ökologischen Lebensmittel an bis zu 30 Minuten vom landwirtschaftlichen Betrieb entfernte Orte transportiert. Die wichtigste Erklärung für die regionalen Unterschiede bei der ökologischen Landwirtschaft scheinen in der vorrangigen Bedeutung der Nachfrage zu liegen. Explicación de las diferencias regionales y locales en la agricultura biológica de Inglaterra y Gales: comparación entre el suroeste de Gales y el sureste de Inglaterra, Regional Studies. En pocos estudios se explica la concentración de la agricultura biológica en regiones específicas de Inglaterra y Gales. En este artículo comparamos el desarrollo de la agricultura biológica en el suroeste de Gales y el sureste de Inglaterra. Mientras que en el suroeste de Gales se hace hincapié en el uso de canales mercantiles principalmente nacionales y el movimiento de productos biológicos a una distancia de más de 60 minutos de la explotación agrícola, en el sureste de Inglaterra se utilizan más los canales mercantiles locales y directos para distribuir alimentos biológicos a no más de 30 minutos de la explotación agrícola. Parece ser que la demanda es el motivo más importante para explicar las diferencias regionales en la agricultura biológica

Entanglement and symmetry in permutation symmetric states

We investigate the relationship between multipartite entanglement and symmetry, focusing on permutation symmetric states. We use the Majorana representation, where these states correspond to points on a sphere. Symmetry of the representation under rotation is equivalent to symmetry of the states under products of local unitaries. The geometric measure of entanglement is thus phrased entirely as a geometric optimisation, and a condition for the equivalence of entanglement measures written in terms of point symmetries. Finally we see that different symmetries of the states correspond to different types of entanglement with respect to SLOCC interconvertibility.Comment: 4 pages, 2 figures. Preliminary versions of some of these results were presented in the QIT 16 workshop in Japan, D. Markham, Proceedings of QIT 16, Japan (2007). Updated to reflect changes for publication: expanded proofs and some new examples give

Quantum Quenches in Free Field Theory: Universal Scaling at Any Rate

Quantum quenches display universal scaling in several regimes. For quenches which start from a gapped phase and cross a critical point, with a rate slow compared to the initial gap, many systems obey Kibble-Zurek scaling. More recently, a different scaling behaviour has been shown to occur when the quench rate is fast compared to all other physical scales, but still slow compared to the UV cutoff. We investigate the passage from fast to slow quenches in scalar and fermionic free field theories with time dependent masses for which the dynamics can be solved exactly for all quench rates. We find that renormalized one point functions smoothly cross over between the regimes.Comment: 40 pages; v2: a bit late, but it includes minor modifications to match published versio

Reduced sensitivity to visual looming inflates the risk posed by speeding vehicles when children try to cross the road

Almost all locomotor animals respond to visual looming or to discrete changes in optical size. The need to detect and process looming remains critically important for humans in everyday life. Road traffic statistics confirm that children up to 15 years old are overrepresented in pedestrian casualties. We demonstrate that, for a given pedestrian crossing time, vehicles traveling faster loom less than slower vehicles, which creates a dangerous illusion in which faster vehicles may be perceived as not approaching. Our results from perceptual tests of looming thresholds show strong developmental trends in sensitivity, such that children may not be able to detect vehicles approaching at speeds in excess of 20 mph. This creates a risk of injudicious road crossing in urban settings when traffic speeds are higher than 20 mph. The risk is exacerbated because vehicles moving faster than this speed are more likely to result in pedestrian fatalities

A randomised controlled trial of total hip arthroplasty versus resurfacing arthroplasty in the treatment of young patients with arthritis of the hip joint

Background: Hip replacement (arthroplasty) surgery is a highly successful treatment for patients with severe symptomatic arthritis of the hip joint. For older patients, several designs of Total Hip Arthroplasty have shown excellent results in terms of both function and value for money. However, in younger more active patients, there is approximately a 50% failure rate at 25 years for traditional implants. Hip resurfacing is a relatively new arthroplasty technique. In a recent review of the literature on resurfacing arthroplasty it was concluded that the short-term functional results appear promising but some potential early disadvantages were identified, including the risk of femoral neck fracture and collapse of the head of the femur. The aim of the current study is to assess whether there is a difference in functional hip scores at one year post-operation between Total Hip Arthroplasty and Resurfacing Arthroplasty. Secondary aims include assessment of complication rates for both procedures as well cost effectiveness. Methods/design: All patients medically fit for surgery and deemed suitable for a resurfacing arthroplasty are eligible to take part in this study. A randomisation sequence will be produced and administered independently. After consenting, all patients will be clinically reviewed and hip function, quality of life and physical activity level will be assessed through questionnaires. The allocated surgery will then be performed with the preferred technique of the surgeon. Six weeks post-operation hip function will be assessed and complications recorded. Three, six and 12 months post-operation hip function, quality of life and physical activity level will be assessed. Additional information about patients' out-of-pocket expenses will also be collected

Supply Disruptions, Asymmetric Information and a Backup Production Option

We study a manufacturer that faces a supplier privileged with private information about supply disruptions. We investigate how risk-management strategies of the manufacturer change, and examine whether risk-management tools are more, or less, valuable, in the presence of such asymmetric information. We model a supply chain with one manufacturer and one supplier, in which the supplier's reliability is either high or low and is the supplier's private information. Upon disruption the supplier chooses between paying a penalty to the manufacturer for the shortfall and using backup production to fill the manufacturer's order. Using mechanism design theory, we derive the optimal contract menu offered by the manufacturer. We find that information asymmetry may cause the less reliable supplier type to stop using backup production while the more reliable supplier type continues to use it. Additionally, the manufacturer may stop ordering from the less reliable supplier type altogether. The value of backup production for the manufacturer is not necessarily larger under symmetric information and, for the more reliable supplier type, it could be negative . The manufacturer is willing to pay the most for information when backup production is moderately expensive. The value of information may increase as supplier types become uniformly more reliable. Thus, higher reliability need not be a substitute for better information.http://deepblue.lib.umich.edu/bitstream/2027.42/58722/1/1110-Damian.pd