Showing papers by "University of Mannheim published in 2010"

Improved Survival with Ipilimumab in Patients with Metastatic Melanoma.

Abstract: Background An improvement in overall survival among patients with metastatic melanoma has been an elusive goal. In this phase 3 study, ipilimumab — which blocks cytotoxic T-lymphocyte–associated antigen 4 to potentiate an antitumor T-cell response — administered with or without a glycoprotein 100 (gp100) peptide vaccine was compared with gp100 alone in patients with previously treated metastatic melanoma. Methods A total of 676 HLA-A*0201–positive patients with unresectable stage III or IV melanoma, whose disease had progressed while they were receiving therapy for metastatic disease, were randomly assigned, in a 3:1:1 ratio, to receive ipilimumab plus gp100 (403 patients), ipilimumab alone (137), or gp100 alone (136). Ipilimumab, at a dose of 3 mg per kilogram of body weight, was administered with or without gp100 every 3 weeks for up to four treatments (induction). Eligible patients could receive reinduction therapy. The primary end point was overall survival. Results The median overall survival was 10.0 months among patients receiving ipilimumab plus gp100, as compared with 6.4 months among patients receiving gp100 alone (hazard ratio for death, 0.68; P<0.001). The median overall survival with ipilimumab alone was 10.1 months (hazard ratio for death in the comparison with gp100 alone, 0.66; P = 0.003). No difference in overall survival was detected between the ipilimumab groups (hazard ratio with ipilimumab plus gp100, 1.04; P = 0.76). Grade 3 or 4 immune-related adverse events occurred in 10 to 15% of patients treated with ipilimumab and in 3% treated with gp100 alone. There were 14 deaths related to the study drugs (2.1%), and 7 were associated with immune-related adverse events. Conclusions Ipilimumab, with or without a gp100 peptide vaccine, as compared with gp100 alone, improved overall survival in patients with previously treated metastatic melanoma. Adverse events can be severe, long-lasting, or both, but most are reversible with appropriate treatment. (Funded by Medarex and Bristol-Myers Squibb; ClinicalTrials.gov number, NCT00094653.)

Can There Ever Be Too Many Options? A Meta-Analytic Review of Choice Overload

Abstract: The choice overload hypothesis states that an increase in the number of options to choose from may lead to adverse consequences such as a decrease in the motivation to choose or the satisfaction with the finally chosen option. A number of studies found strong instances of choice overload in the lab and in the field, but others found no such effects or found that more choices may instead facilitate choice and increase satisfaction. In a meta‐analysis of 63 conditions from 50 published and unpublished experiments (N = 5,036), we found a mean effect size of virtually zero but considerable variance between studies. While further analyses indicated several potentially important preconditions for choice overload, no sufficient conditions could be identified. However, some idiosyncratic moderators proposed in single studies may still explain when and why choice overload reliably occurs; we review these studies and identify possible directions for future research.

Active labor market policy evaluations: a meta-analysis

Abstract: This article presents a meta-analysis of recent microeconometric evaluations of active labour market policies. We categorise 199 programme impacts from 97 studies conducted between 1995 and 2007. Job search assistance programmes yield relatively favourable programme impacts, whereas public sector employment programmes are less effective. Training programmes are associated with positive medium-term impacts, although in the short term they often appear ineffective. We also find that the outcome variable used to measure programme impact matters, but neither the publication status of a study nor the use of a randomised design is related to the sign or significance of the programme estimate.

How General Is Human Capital? A Task-Based Approach

Abstract: This article studies how portable skills accumulated in the labor market are. Using rich data on tasks performed in occupations, we propose the concept of task‐specific human capital to measure empirically the transferability of skills across occupations. Our results on occupational mobility and wages show that labor market skills are more portable than previously considered. We find that individuals move to occupations with similar task requirements and that the distance of moves declines with experience. We also show that task‐specific human capital is an important source of individual wage growth, accounting for up to 52% of overall wage growth.

Industrial Organization: Markets and Strategies

Abstract: Industrial Organization: Markets and Strategies provides an up-to-date account of modern industrial organization that blends theory with real-world applications. Written in a clear and accessible style, it acquaints the reader with the most important models for understanding strategies chosen by firms with market power and shows how such firms adapt to different market environments. It covers a wide range of topics including recent developments on product bundling, branding strategies, restrictions in vertical supply relationships, intellectual property protection, and two-sided markets, to name just a few. Models are presented in detail and the main results are summarized as lessons. Formal theory is complemented throughout by real-world cases that show students how it applies to actual organizational settings. The book is accompanied by a website containing a number of additional resources for lecturers and students, including exercises, answers to review questions, case material and slides.

Corruption and Entrepreneurship: How Formal and Informal Institutions Shape Small Firm Behavior in Transition and Mature Market Economies:

Abstract: This article explores the determinants of corruption in transition economies of the post–Soviet Union, Central–Eastern Europe, and Western industrialized states. We look in–depth at the East–West g...

Loan growth and riskiness of banks.

Abstract: We investigate whether loan growth affects the riskiness of individual banks in 16 major countries. Using Bankscope data from more than 16,000 individual banks during 1997-2007, we test three hypotheses on the relation between abnormal loan growth and asset risk, bank profitability, and bank solvency. We find that loan growth leads to an increase in loan loss provisions during the subsequent three years, to a decrease in relative interest income, and to lower capital ratios. Further analyses show that loan growth also has a negative impact on the risk-adjusted interest income. These results suggest that loan growth represents an important driver of the riskiness of banks.

The Oxford Handbook of Comparative Institutional Analysis

Abstract: It is increasingly accepted that "institutions matter" for economic organization and outcomes. The last decade has seen significant expansion in research examining how institutional contexts affect the nature and behavior of firms, the operation of markets, and economic outcomes. Yet "institutions" conceal a multitude of issues and perspectives. Much of this research has been comparative, and followed different models such as "varieties of capitalism", "national business systems", and "social systems of production". This Handbook explores these issues, perspectives, and models, with the leading scholars in the area contributing chapters to provide a central reference point for academics, scholars, and students. Features Covers models such as 'varieties of capitalism', 'national business systems', and 'social systems of production'. Chapters by leading international scholars Covers issues such as corporate governance, employment, and financial systems Chapters on theory and methodology

multiTree: A computer program for the analysis of multinomial processing tree models.

Abstract: Multinomial processing tree (MPT) models are a family of stochastic models for psychology and related sciences that can be used to model observed categorical frequencies as a function of a sequence of latent states For the analysis of such models, the present article presents a platform-independent computer program called multiTree, which simplifies the creation and the analysis of MPT models This makes them more convenient to implement and analyze Also, multiTree offers advanced modeling features It provides estimates of the parameters and their variability, goodness-of-fit statistics, hypothesis testing, checks for identifiability, parametric and nonparametric bootstrapping, and power analyses In this article, the algorithms underlying multiTree are given, and a user guide is provided The multiTree program can be downloaded from http://psycho3uni-mannheimde/multitree

Removing Multiplicative Noise by Douglas-Rachford Splitting Methods

Abstract: In this paper, we consider a variational restoration model consisting of the I-divergence as data fitting term and the total variation semi-norm or nonlocal means as regularizer for removing multiplicative Gamma noise. Although the I-divergence is the typical data fitting term when dealing with Poisson noise we substantiate why it is also appropriate for cleaning Gamma noise. We propose to compute the minimizers of our restoration functionals by applying Douglas-Rachford splitting techniques, resp. alternating direction methods of multipliers. For a particular splitting, we present a semi-implicit scheme to solve the involved nonlinear systems of equations and prove its Q-linear convergence. Finally, we demonstrate the performance of our methods by numerical examples.

Survey Methods in Multinational, Multiregional, and Multicultural Contexts

Abstract: This book provides up-to-date insight into key aspects of methodological research for comparative surveys. It discusses methodological considerations for surveys that are deliberately designed for ...

Mental Construal and the Emergence of Assimilation and Contrast Effects: The Inclusion/Exclusion Model

Abstract: The inclusion/exclusion model provides an integrative framework for conceptualizing the emergence of assimilation and contrast effects in evaluative judgment The model assumes that feature-based evaluative judgments require a mental representation of the object of judgment (target) and of a standard to which the target is compared Both representations are context sensitive and based on the information that is most accessible at the time The way in which accessible information influences the judgment depends on how it is used Information that is used in forming a representation of the target results in assimilation effects; information that is used in forming a representation of the standard results in contrast effects How information is used depends on (i) individuals' beliefs about whether the information was brought to mind by some irrelevant influence, (ii) the information's perceived representativeness for the target, and (iii) conversational norms that influence the perceived appropriateness of information use We summarize the core assumptions of the inclusion/exclusion model, review empirical evidence bearing on it, and highlight its integrative nature

Cujo: efficient detection and prevention of drive-by-download attacks

Abstract: The JavaScript language is a core component of active and dynamic web content in the Internet today. Besides its great success in enhancing web applications, however, JavaScript provides the basis for so-called drive-by downloads---attacks exploiting vulnerabilities in web browsers and their extensions for unnoticeably downloading malicious software. Due to the diversity and frequent use of obfuscation in these attacks, static code analysis is largely ineffective in practice. While dynamic analysis and honeypots provide means to identify drive-by-download attacks, current approaches induce a significant overhead which renders immediate prevention of attacks intractable.In this paper, we present Cujo, a system for automatic detection and prevention of drive-by-download attacks. Embedded in a web proxy, Cujo transparently inspects web pages and blocks delivery of malicious JavaScript code. Static and dynamic code features are extracted on-the-fly and analysed for malicious patterns using efficient techniques of machine learning. We demonstrate the efficacy of Cujo in different experiments, where it detects 94% of the drive-by downloads with few false alarms and a median run-time of 500 ms per web page---a quality that, to the best of our knowledge, has not been attained in previous work on detection of drive-by-download attacks.

Public Opinion and Executive Compensation

Abstract: We investigate whether public opinion influences the level and structure of executive compensation. During 1992-2008 the negativity of press coverage of CEO pay varied significantly, with stock options being the most criticized pay component. We find that after more negative press coverage of CEO pay firms reduce option grants and increase less contentious types of pay such as salary, while overall compensation does not change. The reduction in option pay after increased press negativity is more pronounced when firms, CEOs and boards have stronger reputation concerns. Our within-firm, within-year identification shows the results cannot be explained by annual changes in accounting rules regarding executive compensation, stock market conditions, or pay mean-reversion.

Secure computation with fixed-point numbers

Abstract: Secure computation is a promising approach to business problems in which several parties want to run a joint application and cannot reveal their inputs. Secure computation preserves the privacy of input data using cryptographic protocols, allowing the parties to obtain the benefits of data sharing and at the same time avoid the associated risks. These business applications need protocols that support all the primitive data types and allow secure protocol composition and efficient application development. Secure computation with rational numbers has been a challenging problem. We present in this paper a family of protocols for multiparty computation with rational numbers using fixed-point representation. This approach offers more efficient solutions for secure computation than other usual representations.

How does liquidity affect government bond yields

Abstract: The paper explores the determinants of yield differentials between sovereign bonds, using euro-area data. There is a common trend in yield differentials, which is correlated with a measure of aggregate risk. In contrast, liquidity differentials display sizeable heterogeneity and no common factor. We propose a simple model with endogenous liquidity demand, where a bond’s liquidity premium depends both on its transaction cost and on investment opportunities. The model predicts that yield differentials should increase in both liquidity and risk, with an interaction term of the opposite sign. Testing these predictions on daily data, we find that the aggregate risk factor is consistently priced, liquidity differentials are priced for a subset of countries, and their interaction with the risk factor is in line with the model’s prediction and crucial to detect their effect.

Position Taking in European Parliament Speeches

Abstract: This article examines how national parties and their members position themselves in European Parliament (EP) debates, estimating the principal latent dimension of spoken conflict using word counts from legislative speeches. We then examine whether the estimated ideal points reflect partisan conflict on a left–right, European integration or national politics dimension. Using independent measures of national party positions on these three dimensions, we find that the corpus of EP speeches reflects partisan divisions over EU integration and national divisions rather than left–right politics. These results are robust to both the choice of language used to scale the speeches and to a range of statistical models that account for measurement error of the independent variables and the hierarchical structure of the data.

How Risky Do I Invest: The Role of Risk Attitudes, Risk Perceptions, and Overconfidence

Abstract: Our study analyzes the determinants of investors' risk taking behavior. We find that investors' risk taking behavior is affected by their subjective risk attitude and by the risk and return of an investment alternative. Our results also suggest that consistent with previous findings in the literature objective or historical return and volatility of a stock are not as good predictors of risk taking behavior as subjective risk and return measures. Moreover, we illustrate that overconfidence or more precisely miscalibration has an impact on risk behavior as predicted by theoretical models. However, our results regarding the effect of various determinants on risk taking behavior heavily depends on the domain the respective determinant is elicited. We interpret this as an indication for an extended domain specificity. In particular with the Markets of Financial Instruments Directive (MiFID) coming into effect we believe practitioners could improve on their investment advising process by incorporating some of the determinants we argue to influence investment behavior.

The Diffusion of Market Orientation Throughout the Organization: A Social Learning Theory Perspective

Abstract: This study examines the diffusion of market orientation as a social learning process to acquire and transfer individual-level market orientation. Central to the diffusion are important work-group members, or envoys. Through their market-oriented action, top managers serve as market-oriented role models to two important types of observers in work groups — formal middle managers and work-group expert peers. These observers in turn become top managers’ envoys to role-model market oriented behavior to frontline employees. Empirical results from a three-level data set from a Fortune 500 company support this perspective. While envoys that are neither market oriented nor identified with the firm are the worst, envoys that are not market oriented but are strongly identified with the firm are also detrimental. Network size hinders the informal route of learning through expert peers but not the formal route through middle managers. By identifying whom the important work-group envoys are and under what conditions certain envoys are likely to be most effective, this study helps managers select the most effective envoys to implement market orientation.

A structured approach to anomaly detection for in-vehicle networks

Abstract: The complexity and connectivity of modern vehicles has constantly increased over the past years. Within the scope of this development the security risk for the in-vehicle network and its components has risen massively. Apart from threats for comfort and confidentiality, these attacks can also affect safety critical systems of the vehicle and therefore endanger the driver and other road users. In this paper the introduction of anomaly detection systems to the automotive in-vehicle network is discussed. Based on properties of typical vehicular networks, like the Controller Area Network (CAN), a set of anomaly detection sensors is introduced which allow the recognition of attacks during the operation of the vehicle without causing false positives. Moreover, important design and application criteria for a vehicular attack detection system are explained and discussed.

Estimation of quantile treatment effects with STATA

Abstract: WARNING: this page is no longer updated. Go to http://www.econ.brown.edu/fac/Blaise_Melly/ to find the current version of the codes. News: This paper will be published by the Stata Journal soon. Therefore, it can nolonger be downloaded from this page. In this paper, we discuss the implementation of various estimators proposed to estimate quantile treatment effects (QTE). We distinguish four cases: conditional and unconditional QTE with exogenous or endogenous treatment variable. Therefore, the ivqte command covers four different estimators: the classical quantile regression estimator of Koenker and Bassett (1978) extended to heteroskedasticity consistent standard errors, the IV quantile regression estimator of Abadie, Angrist, and Imbens (2002), the estimator for unconditional QTE proposed by Firpo (2007), and the IV estimator for unconditional QTE proposed by Frolich and Melly (2007). The implemented IV procedures estimate the causal effects for the sub-population of compliers and are well-suited for binary instruments only. This command also provides analytical standard errors and various options for nonparametric estimation. As a by-product, the command locreg implements local linear and local logit estimators for mixed data (continuous, ordered discrete, unordered discrete and binary regressors).

Customer Satisfaction, Analyst Stock Recommendations, and Firm Value

Abstract: Although managers are interested in the financial value of customers and researchers have pointed out the importance of stock analysts who advise investors, no studies to date have explored the implications of customer satisfaction for analyst stock recommendations. Using a large-scale longitudinal data set, the authors find that positive changes in customer satisfaction not only improve analyst recommendations but also lower dispersion in those recommendations for the firm. These effects are stronger when product market competition is high and financial market uncertainty is large. In addition, analyst recommendations at least partially mediate the effects of changes in satisfaction on firm abnormal return, systematic risk, and idiosyncratic risk. Analyst recommendations represent a mechanism through which customer satisfaction affects firm value. Thus, if analysts pay attention to Main Street customer satisfaction, Wall Street investors should have good reason to listen and follow. Overall, thi...

Bankers on the Boards of German Firms: What They Do, What They Are Worth, and Why They Are (Still) There

Abstract: In this paper, we analyze the role of bankers on the boards of German non-financial companies. We assemble a unique panel data set for 137 firms and 11 banks for the period from 1993 to 2005 and investigate if bankers act as monitors of their equity interests or their interests as lenders, as capital market experts, or if they help to advance the commercial banking services and the investment banking services of their banks. We find convincing evidence that bankers promote their M&A advisory services, but we find no or little evidence for all other hypotheses that have been formulated in the literature. Our main conclusions are that bankers extract private benefits from their board seats and that banks benefit because bankers on the board become industry experts. Non-financial firms do not benefit because bank representation on their boards reduces their valuations. JEL classifications: G21, G34

Improved primitives for secure multiparty integer computation

Abstract: We consider a collection of related multiparty computation protocols that provide core operations for secure integer and fixed-point computation. The higher-level protocols offer integer truncation and comparison, which are typically the main performance bottlenecks in complex applications. We present techniques and building blocks that allow to improve the efficiency of these protocols, in order to meet the performance requirements of a broader range of applications. The protocols can be constructed using different secure computation methods. We focus on solutions for multiparty computation using secret sharing.

Belief elicitation in experiments: is there a hedging problem?

Abstract: Belief-elicitation experiments usually reward accuracy of stated beliefs in addition to payments for other decisions. But this allows risk-averse subjects to hedge with their stated beliefs against adverse outcomes of the other decisions. So can we trust the existing belief-elicitation results? And can we avoid potential hedging confounds? We propose an experimental design that theoretically eliminates hedging opportunities. Using this design, we test for the empirical relevance of hedging effects in the lab. Our results suggest that hedging confounds are not a major problem unless hedging opportunities are very prominent. If hedging opportunities are transparent, and incentives to hedge are strong, many subjects do spot hedging opportunities and respond to them. The bias can go beyond players actually hedging themselves, because some expect others to hedge and best respond to this.

DOG1 and CD117 are the antibodies of choice in the diagnosis of gastrointestinal stromal tumours.

Abstract: Novelli M, Rossi S, Rodriguez-Justo M, Taniere P, Seddon B, Toffolatti L, Sartor C, Hogendoorn P C W, Sciot R, Van Glabbeke M, Verweij J, Blay J Y, Hohenberger P, Flanagan A & Dei Tos A P (2010) Histopathology57, 259–270 DOG1 and CD117 are the antibodies of choice in the diagnosis of gastrointestinal stromal tumours Aims: The histopathological diagnosis of gastrointestinal stromal tumours (GIST) is typically made based on a combination of clinical and morphological features supported by immunohistochemistry studies. The aim of this study was to examine the staining quality, sensitivity, specificity and utility of antibodies used commonly in GIST diagnosis. Methods and results: Immunohistochemistry with a panel of antibodies [CD117, DOG1, protein kinase C (PKC)-theta, nestin, CD34, smooth muscle actin (SMA), desmin, S100 and CD171] was performed on whole sections from 187 GIST and 29 gastrointestinal mesenchymal tumours, and on several microarrays including 355 GISTs and 120 soft tissue sarcomas. Results showed that DOG1 and CD117 were the most sensitive and specific antibodies used in GIST diagnosis. PKC-theta and nestin were sensitive, but less specific, also staining other spindle cell tumours commonly considered in the differential diagnosis of GIST. CD34 staining was less sensitive than many of the other antibodies and of limited aid in diagnosis. The smooth muscle markers SMA and desmin, together with the neural marker S100, were unhelpful in confirming a diagnosis of GIST, but were particularly useful in the exclusion/diagnosis of other gastrointestinal mesenchymal tumour types. Conclusions: In the majority of histologically suspected GISTs a combination of CD117 and DOG1 immunostaining is sufficient to confirm the histological diagnosis.