A note on the existence of unique equivalent martingale measures in a Markovian setting

Simple sufficient conditions for the existence of a unique equivalent martingale measure are provided. Furthermore, these conditions give us a handle on situations where an equivalent martingale measure cannot exist. The existence of a unique equivalent martingale measure is of relevance to problems in mathematical finance. Two examples of models for which the question of existence was unresolved are studied. By means of our results existence of a unique equivalent measure up to an explosion time is proved.     

Impacts of Declining U.S. Retail Beef Demand on Farm-Level Beef Prices and Production

A systems model was estimated to determine the effects of declining U.S. retail beef demand on farm-level beef prices and production. Retail beef demand declined by nearly 66% from 1976 to 1999. Results indicate autonomous shifts in retail demand significantly impacted farm-level demands and production. Based on equilibrium multipliers, the 1976–99 reduction in beef demand decreased real slaughter cattle prices and production by 32.1% and 11.2%, respectively. Real feeder cattle prices and production decreased by 8.0% and 22.6%, respectively. Combining the decreases in farm prices and production, slaughter and feeder cattle producers experienced a real revenue reduction of $13.3 billion (61%) due to the long-term decline in demand.     

神府—东胜矿区沙漠化趋势预测与防治措施

神府－东胜矿区在特定的自然地质环境和人为因素的影响下，土地沙漠化呈不断扩展的演化趋势。矿区大规模的开发建设，更加速了沙漠化进展。本文利用典型地段的沙漠化发展速率，依据矿区总体设计规模，对矿区自然沙漠化趋势和开矿新增沙漠化土地面积进行了定量预测，并提出了相应的防治措施。     

A Global Ex-vessel Fish Price Database: Construction and Applications

Synopsis We describe the first effort at creating a global ex-vessel fish price database, which is required for understanding the economic behavior of participants in the world’s fisheries. We demonstrate potential applications of the database by linking it to a spatially defined catch database, which makes it possible to attach landed values to species in both time and space. This is the first database available publicly where interested members of the public, researchers and managers can easily find and access ex-vessel prices of the world’s major commercial fish species. Preliminary results indicate that the average real price of a number of species have declined between 1950 and 2002. The estimated landed value of fish globally, in year 2000 dollars, was about US$24 billion in 1950. It increased steadily to about US$90 billion in the early 1970s, reached a peak of US$100 billion at the end of the 1980s, and declined to about US$80 billion in 2000. The top 15 fishing countries cumulatively account for 79% of total real landed value, with Japan leading, even though the value of its landings has been declining.      

基于供应链管理的企业营销渠道创新

传统渠道链的内在缺陷和新竞争模式的外在压力迫使企业必须通过渠道创新以获得新的利润和竞争力。本文在借鉴供应链管理优势的基础上,从组织结构、成员关系和管理模式创新三方面入手,提出渠道构建的逆向模式,以实现渠道的系统优化及各成员的长远利益最大,并使得市场的覆盖更为有效。     

Recursive utility with unbounded aggregators

A new framework is presented for the study of the existence and uniqueness of solutions to the Koopmans’ equation in the unbounded case, that is based on the contraction mapping approach. In the bounded below case with bounded consumption streams, uniqueness of the solution in the whole class of weak-star continuous utility functions is obtained. When the aggregator is unbounded below and/or consumption streams are unbounded, existence of a weak-star continuous solution is shown, and a simple criterium to check the sufficient conditions for existence is provided. Juan Pablo Rincón-Zapatero and Carlos Rodríguez-Palmero gratefully acknowledge financial support by the Ministerio de Educación y Ciencia and FEDER funds under Research Projects MTM2005-06534 and SEJ2005-08709/ECON, respectively, and by Consejería de Educación de la Junta de Castilla y León under Research Projects VA99/04 and VA017B05, respectively. This paper has substantially benefited from the comments of an anonymous referee. Particular and special thanks are due to Robert Becker for his very helpful comments and valuable suggestions.     

由临街地价推算区片价的方法探讨

如何利用临街样点地价推算区片平均地价及基准地价始终是城镇基准地价评估的一个难点。文章利用赤峰市的实际调查数据,分别采用临街贡献率和面积加权两种方法推算区片平均地价,并采用回归分析方法探讨区片价与临街地价之间的关系,结果证明两种方法所推算的区片平均价是基本一致的,而且区片价与临街地价之间呈“反S”曲线关系。     

Credit Risk Research: Review and Agenda

This article provides a comprehensive review of scholarly research on credit risk measurement during the last 57 years applying bibliometric citation analysis and elaborates an agenda for future research. The bibliography is compiled using the Institute for Scientific Information (ISI) Web of Science (WOS) database and includes all articles with citations over the period 1960–2016. Specifically, the review is carried out using 1695 articles across 72 countries published in 442 journals by 2928 authors. The findings suggest that credit risk research is multifaceted and can be classified into six streams: (1) defaultable security pricing, (2) default intensity modeling, (3) comparative analysis of credit models, (4) comparative analysis of credit markets, (5) credit default swap (CDS) pricing, and (6) loan loss provisions. The article contributes through synthesizing and identifying existing as well as emerging research streams.     

GPS在土地测绘中的应用

在经济飞速发展的21世纪,土地测绘的技术也在快速发展着。因为该技术应用于各个领域,其中,GPS技术起到了十分关键的作用,不仅为各个领域的发展提供了充足的准备和保障,也就奠定了GPS成为最基础的科学的地位。     

Hybridizing local and generic information to model cropping system spatial distribution in an agricultural landscape

For quantitative water management, fine analysis of spatial and temporal interactions between cropping systems and water resources helps identify time and site-specific withdrawal situations. However, it is a methodological challenge to provide fine-resolution analyses at the scale of large watersheds used for crises management. In this study, we present a methodology based on multiple methods and mixed sources of information to finely model an agricultural landscape (AL) that represents the spatial distribution of cropping systems. Our approach is based on progressively hybridizing databases and local actors' and experts' knowledge to produce a spatially explicit and dynamic model. The Land Parcel Identification System database, which resulted from the European Common Agricultural Policy, is crucial for our method since it provides the spatial and temporal basis of our model (i.e., geographic delineation of islets and information about crop sequences). Local knowledge is used to identify factors determining spatial distribution of cropping systems and to build a generic model that simulates farmers' crop-management strategies. The model was qualitatively and quantitatively evaluated using a multi-agent simulation platform (MAELIA). We asked local experts on quantitative water management to evaluate the ability of the platform to reproduce intra- and inter-annual dynamics at different levels when using our model of the AL as input. The experts were satisfied with the results; they validated the predicted dynamics of the variables, and some discussed the objectivity of the values. We discuss the method’s contribution to current challenges in modeling large agricultural areas and the associated tradeoffs. The approach is promising for policy makers who wish to develop integrated, locally adapted land-management strategies.