A METHOD FOR PRICING AMERICAN OPTIONS USING SEMI‐INFINITE LINEAR PROGRAMMING

We introduce a new approach for the numerical pricing of American options. The main idea is to choose a finite number of suitable excessive functions (randomly) and to find the smallest majorant of the gain function in the span of these functions. The resulting problem is a linear semi‐infinite programming problem, that can be solved using standard algorithms. This leads to good upper bounds for the original problem. For our algorithms no discretization of space and time and no simulation is necessary. Furthermore it is applicable even for high‐dimensional problems. The algorithm provides an approximation of the value not only for one starting point, but for the complete value function on the continuation set, so that the optimal exercise region and, for example, the Greeks can be calculated. We apply the algorithm to (one‐ and) multidimensional diffusions and show it to be fast and accurate.     

Leveraging purchase regularity for predicting customer behavior the easy way

The valuation of future customer activity is a mainstay of any organization seeking to efficiently manage its customer portfolio. In the area of customer-base analytics, the ongoing race for predictive power has yielded a large corpus of research to assist managers in this respect. Approaches in the tradition of stochastic models have been particularly successful because they rely only on easy-to-compute key metrics and integrate them within a parsimonious probability-modeling framework. Recent advances in this field have demonstrated that incorporating the timing regularity of past purchases can improve predictive accuracy relative to purely recency/frequency-based approaches. This paper expands that idea and introduces generalizations of a well-established probability model, the BG/NBD (Fader et al., 2005a), by replacing the exponential with a more flexible Erlang-k interarrival timing process. The resulting model variants are capable of leveraging regularity while retaining almost the same level of data requirements and algorithmic efficiency. Using extensive simulation studies and six data sets covering a wide range of empirical settings the authors demonstrate substantial improvements in predictive accuracy against the baseline models and performance gains close to or on par with a more complex model alternative. The availability of efficient and easily accessible implementations of the new model variants in the R-package BTYDplus allows marketing analysts to apply them in large-scale scenarios of data-rich environments on a continuous basis.     

Scope and patterns of tourist injuries in the European Union

European Union (EU) countries are among the leading tourist destinations in the world. Despite growing consumer demands on the safety of travelling, injuries amongst tourists remain an essentially invisible problem. Unique national and regional data sources are the only means by which the important negative impact of injuries on the health of non-domestic tourists in the EU-15 is underlined. With an estimated number of 3800 tourists dying each year, injuries account for up to 30% of fatalities during vacation. This toll reflects an increased risk of mortality in tourists compared to the domestic population. Amendments to national and EU health and injury monitoring are suggested in order to enable authorities to examine personal risks to travellers in more detail.     

Verbraucherpolitische Konzeptionen und Programme in der Bundesrepublik Deutschland

Zusammenfassung Die Notwendigkeit einer expliziten Verbraucherpolitik ist in der Bundesrepublik Deutschland in den letzten Jahren zunehmend anerkannt worden. Dies dokumentiert sich zum einen in einigen Ansätzen zur Institutionalisierung der Verbraucherpolitik, zum anderen in einer programmatischen Diskussion, an der inzwischen die wichtigsten gesellschaftlich relevanten Gruppen teilnehmen. Analysiert und vergleicht man die verbraucherpolitischen Vorhaben amtlicher Stellen sowie die von Arbeitgeberverbänden, Gewerkschaften und politischen Parteien entwickelten Konzeptionen, so zeigt sich ein uniformes Denkschema, das dem Paradigma Markt und Wettbewerb verhaftet ist. Unterschiede offenbaren sich lediglich in den jeweils präferierten Maßnahmen. Alle Konzeptionen folgen — wenn auch mit unterschiedlicher Gewichtung — den beiden handlungsanleitenden Argumentationsschemata »Ergänzung der Wettbewerbspolitik durch Verbraucherschutz und -information« sowie »Gegenmachtbildung und Interessenvertretung«. Der Gedanke an direktere Kommunikationsformen sowie an eine frühzeitige Einflußnahme der Konsumenten auf das Güterangebot findet sich in keinem der Programme.

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Conceptions of consumer policy in the Federal Republic of Germany

The necessity for an explicit public consumer policy has found increased acceptance during the last couple of years. This is reflected both in attempts to institutionalize consumer policy and in a programmatic discussion in which many relevant social groups are participating. The analysis of consumer oriented plans and models of governmental agencies, employers' associations, trade unions, and political parties reveals uniform thought, rooted in the paradigm of market and competition. Differences can be detected only in the recommended measures. Basically all concepts fall under one of the following categories of argumentation: Competition policy needs completion by consumer protection and consumer information or There is a need for consumer countervailing power and consumer lobbyism. The existing plans are characterized by mere auxiliary means to stimulate consumers' reactions. The considerations of a direct communication between producers and consumers and of an early influence by consumers on manufacturers' product decisions are, however, not included in any of the programmes.

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Christine Czerwonka und Günter Schöppe sind Wissenschaftliche Mitarbeiter am Institut für Markt und Plan der Johann Wolfgang Goethe-Universität, 6000 Frankfurt/Main, Senckenberganlage 31.     

Going Beyond Impact Factors: A Survey‐based Journal Ranking by Agricultural Economists

A consistent and comprehensive ranking of journals relevant for agricultural economists cannot rely on impact factors for at least two major reasons: (i) the scientific database by Thomson Reuters, on which the standard impact factor is based, includes only a very limited number of relevant journals; (ii) the standard impact factor cannot be compared across research fields of different sizes. Survey‐based journal rankings may overcome these problems. We report on such a survey‐based ranking initiated by the Agricultural Economics Associations of Germany and Austria. Results of the ranking and a classification of journals, i.e. a rating, are provided for 160 selected journals. Scientific quality is assessed by an index based on the researchers’ perception of the quality standards of each journal and of the quality of its published articles. The survey‐based ranking allows a much more comprehensive and consistent ranking than the impact factor, as specific agricultural economics journals can be directly compared with neighbouring economic and interdisciplinary journals to which agricultural economists submit their work. The low impact factors of core agricultural economics journals are put into perspective. The scientific quality of the top agricultural economics journals is assessed as being rather high and above most of the relevant interdisciplinary journals from agricultural and food sciences that are typically characterised by higher impact factors. Agricultural economists’ perceptions on the scientific quality of the journals vary more across journals than perceptions of their relevance.     

Sustainable agricultural intensification: the role of cardamom agroforestry in the East Usambaras,Tanzania

The East Usambaras in Tanzania are a tropical biodiversity hotspot where current agricultural management practices pose threats to forest conservation and development objectives. Promoting sustainable agricultural intensification (SAI) would improve long-term productivity and reduce pressure on forest reserves. The study objective was to identify household-level characteristics that influence adoption of improved management practices, specifically soil replenishment practices, in order to identify opportunities and constraints to scaling up SAI to landscape level. First, three common farming systems and a fourth agroforestry (AF) model were developed to estimate the relative profitability of incorporating fallow, manure, and non-timber forest product activities. Next, household surveys were conducted and a logistic regression analysis was used to measure the influence of socioeconomic characteristics, physical and financial assets, tenure security, and plot-specific attributes on adoption of soil replenishment practices that were specified in the model. Findings showed that the AF model was financially competitive but raises opportunity costs to labour when compared to common systems. Marital status, household size, remittances, credit access, and tenure security significantly influenced adoption of fallow and applying organic inputs. Significant plot-specific attributes included perceived fertility and distance from the homestead. Policies to scale up SAI should consider these factors and emphasize improving markets for AF species and extension services.     

Between dependence and deprivation: The interlocking nature of land alienation in Tanzania

Studies of accumulation by dispossession in the Global South tend to focus on individual sectors, for example, large‐scale agriculture or nature conservation. Yet smallholder farmers and pastoralists are affected by multiple processes of land alienation. Drawing on the case of Tanzania, we illustrate the analytical purchase of a comprehensive examination of dynamics of land alienation across multiple sectors. To begin with, processes of land alienation through investments in agriculture, mining, conservation, and tourism dovetail with a growing social differentiation and class formation. These dynamics generate unequal patterns of land deprivation and accumulation that evolve in a context of continued land dependency for the vast majority of the rural population. Consequently, land alienation engenders responses by individuals and communities seeking to maintain control over their means of production. These responses include migration, land tenure formalization, and land transactions, that propagate across multiple localities and scales, interlocking with and further reinforcing the effects of land alienation. Various localized processes of primitive accumulation contribute to a scramble for land in the aggregate, providing justifications for policies that further drive land alienation.     

Evaluating spatial and temporal variation in agricultural output elasticities in Turkey

This study evaluates spatial variation in the relationship between agricultural output and input use across Turkey. The potential impact of the national agricultural policy reform introduced in 2001 on the spatial variation in agricultural output elasticities across the country was explored. By applying a spatial production function to the province‐level data in 2000 and 2007, spatial heterogeneity in the variance of provincial total factor productivity and the input factor‐output elasticities was identified across the country. Results show that the disparities in agricultural activities and geographic conditions affected return from input factors. Empirical findings from a spatial spillover model also suggest that changes in the input factor‐output elasticities varied significantly across Turkey between 2000 and 2007, after the policy reform. Results suggest that future policy reform that recognizes regional comparative advantage through understanding the geographic heterogeneity of the agricultural sector is important for enhancing Turkey's agricultural output.