Bandwidth selection for kernel density estimation: a review of fully automatic selectors

On the one hand, kernel density estimation has become a common tool for empirical studies in any research area. This goes hand in hand with the fact that this kind of estimator is now provided by many software packages. On the other hand, since about three decades the discussion on bandwidth selection has been going on. Although a good part of the discussion is about nonparametric regression, this parameter choice is by no means less problematic for density estimation. This becomes obvious when reading empirical studies in which practitioners have made use of kernel densities. New contributions typically provide simulations only to show that the own selector outperforms some of the existing methods. We review existing methods and compare them on a set of designs that exhibit few bumps and exponentially falling tails. We concentrate on small and moderate sample sizes because for large ones the differences between consistent methods are often negligible, at least for practitioners. As a byproduct we find that a mixture of simple plug-in and cross-validation methods produces bandwidths with a quite stable performance.     

When and with whom to cooperate? Investigating effects of cooperation stage and type on innovation capabilities and success

In times of saturated markets and decreasing product life cycles, the continuous development and successful launch of innovations are essential for profit-oriented organizations of any kind. Interorganizational cooperation enables companies to get better access to knowledge and capabilities in order to generate and successfully introduce innovations. While scientific research and management practice have acknowledged the importance of cooperation, little research effort is dedicated to empirically determine the effectiveness of cooperation intensity within different stages of the innovation process (cooperation stage) and with different partners (cooperation type). This article aims to fill these gaps by empirically examining the effects of cooperation intensity with different kinds of partners (horizontal, vertical and institutional cooperation) in different stages of new product development (concept and product development as well as implementation stage) on innovation capabilities and success of individual companies. Drawing upon a sample of 154 high-tech companies from the German B-2-B sector, our results reveal that it is in general beneficial for a company to cooperate. However, cooperation in concept and product development primarily improves a company's innovation capabilities while cooperation in the implementation stage primarily enhances innovation success of a company. With respect to cooperation type, vertical, horizontal as well as institutional cooperation significantly enhance innovation capabilities and success of a company. However, cooperation with institutional partners was found to be the most important contributor throughout all stages.     

Effectuation or causation as the key to corporate venture success? Investigating effects of entrepreneurial behaviors on business model innovation and venture performance

Corporate Venturing sets the stage for entrepreneurial behavior in order to create business model innovation (BMI). Moreover, prior literature indicates the importance of BMI as a source of performance advantage, especially in growing industries. However, an empirical examination of the effectiveness of entrepreneurial behaviors for achieving BMI is still lacking. Hence, this study investigates the effectiveness of effectuation and causation as primary entrepreneurial logics to create BMI. Analyzing data obtained from 128 corporate ventures with partial least squares structural equation modeling, the effectiveness of both entrepreneurial logics for BMI with respect to different industry growth levels is clarified: The results point out that both behaviors lead to BMI in situations of moderate industry growth while effectuation (causation) is more effective in high (low) industry growth settings. Furthermore, the results point out that BMI in turn enhances corporate venture performance. Thus, corporate entrepreneurs should carefully align their entrepreneurial approach with industry growth projections to effectively develop BMI and achieve high venture performance.     

Hermann Kotthoff und Ingrid Matthäi: Vom Kombinat zum Kleinbetrieb. Die Entstehung einer mittelständischen Industrie. Ein deutsch-tschechischer Vergleich

Ohne Zusammenfassung     

Limits of Applicability for the Deterministic Approximation of the Two-Step Clonal Expansion Model

Motivated by a hypothesis published recently, the limits of applicability of the deterministic approximation of the two-step clonal expansion model are investigated. The approximate hazard increases unlimited, while the exact hazard is approaching a constant value. The approximate solution becomes inapplicable for hazards in the order of that constant rate. When the initiation rate is much larger than the cell division rate, the survival rate is small when the approximation becomes inapplicable. The simplicity of the exact solutions suggests using them in all situations.