Multi-level Monte Carlo methods for the approximation of invariant measures of stochastic differential equations

We develop a framework that allows the use of the multi-level Monte Carlo (MLMC) methodology (Giles in Acta Numer. 24:259–328, 2015. https://doi.org/10.1017/S096249291500001X) to calculate expectations with respect to the invariant measure of an ergodic SDE. In that context, we study the (over-damped) Langevin equations with a strongly concave potential. We show that when appropriate contracting couplings for the numerical integrators are available, one can obtain a uniform-in-time estimate of the MLMC variance in contrast to the majority of the results in the MLMC literature. As a consequence, a root mean square error of $$\mathcal {O}(\varepsilon )$$ is achieved with $$\mathcal {O}(\varepsilon ^{-2})$$ complexity on par with Markov Chain Monte Carlo (MCMC) methods, which, however, can be computationally intensive when applied to large datasets. Finally, we present a multi-level version of the recently introduced stochastic gradient Langevin dynamics method (Welling and Teh, in: Proceedings of the 28th ICML, 2011) built for large datasets applications. We show that this is the first stochastic gradient MCMC method with complexity $$\mathcal {O}(\varepsilon ^{-2}|\log {\varepsilon }|^{3})$$, in contrast to the complexity $$\mathcal {O}(\varepsilon ^{-3})$$ of currently available methods. Numerical experiments confirm our theoretical findings.     

Getting tuned in to those who are different: The role of empathy as mediator between diversity and performance

We present a theoretical model on the processes that mediate and moderate the diversity-performance relationship. Past research on this topic—for example the categorization elaboration model (van Knippenberg et al. 2004)—has often focused on information elaboration as mediator. Complementing this cognitive perspective, we propose that group diversity can also stimulate group members to engage with each other emotionally, resulting in higher levels of empathy—an emotional state which arises from the comprehension and apprehension of fellow group members’ emotional state. Empathy, in turn, is likely to enhance performance through processes within a single group member and through processes between group members. At the core of the model lies the proposition that group- as well as individual-level empathy mediate the relationship between diversity of organizational units and the performance of individual members and groups at large (multilevel mediation). Furthermore, we specify moderating conditions for the relationship between diversity and empathy. Diversity beliefs and diversity climates are introduced as second-order moderators.     

Optimal stimulation level theory, exploratory consumer behaviour and product adoption: an analysis of underlying structures across product categories

Research of the last decades focused on answering several questions in view of optimum stimulation theory. Which variables do influence general explorative tendencies such as risk taking, variety seeking, or curiosity-motivated behaviour and how do the general explorative tendencies effect the willingness to choose new or familiar products on a repurchase occasion? The approach of this research is the attempt to analyse a wide range of variables, which have successfully been tested to influence innovative behaviour, within one simultaneous model. This research is applied across different product-categories. It is confirming the nomological validity of OSL-theory including some contextual variables by attesting a principal consistency between all (six) models that have been established throughout the range of several examined product categories. The parameters between inherent factors do not contradict when comparing the single models with each other, parameter values do only differ slightly according to category-specific peculiarities. As a consequence of these results, an overall fairly good picture is drawn of what is behind the keenness for innovations of early adopters in general (regardless of the product category).     

Dividend yield and stability versus performance on the German stock market: a descriptive study

It is often examined in the literature whether the dividend yields of stocks correlate with their total returns. This paper analyzes the effect of dividend yield on return as well as on risk and on performance of stocks and stock portfolios on the German market. Not only the influence of dividend yield but also of dividend stability is subject to our analysis. Furthermore, tax aspects are considered. However, this study should rather be seen as an empirical analysis of the influence of dividends as a capital market anomaly than a theoretical based validation approach. Our data set comprises daily adjusted stock prices and dividend payment data from the German capital market over the period 3 January 2000–31 July 2008. This period was characterized by a high volatility of the stock market. In addition to the existing literature examining mainly the long-term influence of dividend yields, we also want to find out whether stocks with high and stable dividend payments are able to reduce the risk of a stock investment in short time periods characterized by extreme conditions. We use blue chips (DAX), stocks of medium-sized companies (MDAX), and stocks of technology firms (TecDAX). Our findings suggest that stock performance generally improves with an increasing dividend yield, where this result is actually based on risk reduction instead of a higher return. However, this risk reduction diminishes with an increasing degree of diversification.     

Structural and contextual approaches to ambidexterity: A meta-analysis of organizational and environmental contingencies

This meta-analysis examines the conditions under which structural and contextual approaches help balance exploration and exploitation. Drawing on heterogeneous samples of prior ambidexterity studies, we apply moderated meta-analytic regression methods to 33,492 organizations sampled in 114 primary studies from 1991 to 2017 to test a contingency model. Our findings suggest that structural separation helps firms of all sizes to balance exploration and exploitation, and that structural separation is more conducive for balancing exploration and exploitation in high technology environments. Also, avoiding a structural separation approach benefits service firms. As research on ambidexterity enters the maturity stage we discuss the implications for future theory development, methodology, and for managers interested in developing ambidextrous organizations.     

The illusion of independence: Spun-off firms’ risk-taking as a function of status and attachment to the parent firm

This paper examines the post-divestiture behavior of spun-off firms. Drawing on the spin-off literature and middle-status conformity theory, we argue that spun-off firms—as newly independent and publicly traded firms—tend to limit their risk-taking behavior to match the expectations of a crucial audience, i.e., security analysts. Following the logic of middle-status conformity theory, we hypothesize that firms with mid-level status are particularly susceptible to analysts' pressures, whereas high- and low-status firms are free to take greater risks. Crucially, however, we propose that this relationship is less pronounced for spun-off firms that are more attached to their parent firms, as formal and informal linkages between these two types of firms can endure beyond the separation and limit spun-off firms' independence. Using a dataset of 102 spin-off transactions occurring between 1995 and 2010, we find empirical support for a U-shaped relationship between spun-off firms' status and risk-taking. This relationship is attenuated when spun-off firms are more attached to their parents. We contribute to the spin-off literature by demonstrating that a spun-off firm's post-divestiture behavior is determined by the capital market audience's expectations and the attachment to the parent firm. In so doing, we also contribute to the literature on middle-status conformity theory by identifying a boundary condition of the theory. Additionally, we make a methodological contribution by combining ideas from the spin-off and institutional theory literature to develop a particularly comprehensive measure of attachment.     

How does consumer age affect the desire for new products and brands? A multi-group causal analysis

Marketing lacks comprehension on the increasingly important segment of mature consumers in regard to their behavior and respective reasons for certain behavior. This study on the desire for alternative products or brands within the domain of fast moving consumer goods was capable of verifying differences among age-groups. While the keenness for cross-buying increases with age, the desire for switching to other familiar brands than the one usually purchased, and the desire for switching to new brand alternatives decrease with age; Thus indicating age-patterns in product category-specific innovativeness and variety seeking. The study also considers a wide range of behavioral determinants such as product satisfaction, product involvement, category experience, perceived purchase risk etc. mediating the effect of age on these desires, giving a fairly good picture of the unveiled causes for the age group differences. Furthermore, the issue of age potentially operating as a moderating variable on the effects of the behavioral determinants on the desires for product and brand alternatives found consideration in this study, but was proven to be of marginal relevance.