Transformation boosting machines

Statistics and Computing - The broad class of conditional transformation models includes interpretable and simple as well as potentially very complex models for conditional distributions. This...     

Boosting techniques for nonlinear time series models

Many of the popular nonlinear time series models require a priori the choice of parametric functions which are assumed to be appropriate in specific applications. This approach is mainly used in financial applications, when sufficient knowledge is available about the nonlinear structure between the covariates and the response. One principal strategy to investigate a broader class on nonlinear time series is the Nonlinear Additive AutoRegressive (NAAR) model. The NAAR model estimates the lags of a time series as flexible functions in order to detect non-monotone relationships between current and past observations. We consider linear and additive models for identifying nonlinear relationships. A componentwise boosting algorithm is applied for simultaneous model fitting, variable selection, and model choice. Thus, with the application of boosting for fitting potentially nonlinear models we address the major issues in time series modelling: lag selection and nonlinearity. By means of simulation we compare boosting to alternative nonparametric methods. Boosting shows a strong overall performance in terms of precise estimations of highly nonlinear lag functions. The forecasting potential of boosting is examined on the German industrial production (IP); to improve the model’s forecasting quality we include additional exogenous variables. Thus we address the second major aspect in this paper which concerns the issue of high dimensionality in models. Allowing additional inputs in the model extends the NAAR model to a broader class of models, namely the NAARX model. We show that boosting can cope with large models which have many covariates compared to the number of observations.     

State Capacity,Conflict, and Development

The absence of state capacities to raise revenue and to support markets is a key factor in explaining the persistence of weak states. This paper reports on an ongoing project to investigate the incentive to invest in such capacities. The paper sets out a simple analytical structure in which state capacities are modeled as forward looking investments by government. The approach highlights some determinants of state building including the risk of external or internal conflict, the degree of political instability, and dependence on natural resources. Throughout, we link these state capacity investments to patterns of development and growth.     

Twin Boosting: improved feature selection and prediction

We propose Twin Boosting which has much better feature selection behavior than boosting, particularly with respect to reducing the number of false positives (falsely selected features). In addition, for cases with a few important effective and many noise features, Twin Boosting also substantially improves the predictive accuracy of boosting. Twin Boosting is as general and generic as (gradient-based) boosting. It can be used with general weak learners and in a wide variety of situations, including generalized regression, classification or survival modeling. Furthermore, it is computationally feasible for large problems with potentially many more features than observed samples. Finally, for the special case of orthonormal linear models, we prove equivalence of Twin Boosting to the adaptive Lasso which provides some theoretical aspects on feature selection with Twin Boosting.     

Participation in ‘big style’: first observations at the German citizens’ dialogue on future technologies

In 2010, the German Federal Ministry of Education and Research started a series of citizens?? dialogues on future technologies. In the context of the German history of public participation in technology-oriented policy making, these dialogues are unique for at least two reasons: The Federal Ministry retains the responsibility for the entire process and is heavily involved in its planning, organization and communication, and the number of participants and process elements is significantly higher than in most other participative events. The paper presents insights into the political background of the citizens?? dialogues, its general concept as well as first observations from the dialogue rounds on energy and high-tech medicine. In addition, it discusses reactions of other political actors and expectations regarding legitimacy and representativeness of the dialogue results.     

Between the Public and the State: The Shipping Lobby's Strategies against US Immigration Restrictions 1882–1917

Based on Freeman's model of interest group‐driven migration policies, the article gives a qualitative inside look on a neglected actor during the formative years of US immigration reform. It analyzes the central role of the shipping companies in coordinating the pro‐immigration campaign with and against other interest groups. Their lobbying is divided into two complementary sections: inside top‐down efforts (lobbyists) to influence legislators and outside bottom‐up efforts (migrant communities and the press) to mobilize the public. It assesses the importance of public opinion in their lobby campaigns and the shipping companies’ success in delaying far‐reaching restrictions until 1917.     

Varieties of Democracy: Interest Groups and Corporatist Committees in Scandinavian Policy Making

Corporatism may be seen as variety of capitalism in which specific structural prerequisites such as unionization, centralization, and strong states combined with bargaining and concertation produce certain economic outputs. Corporatism may also be seen as a variety of democracy in which interest groups are integrated in the preparation and/or implementation of public policies. Departing in the last position, we measure the strength of Scandinavian corporatism by the involvement of interest groups in public committees, councils, and commissions. Corporatism in relation to the preparation of policy has gone down in all three Scandinavian countries whereas corporatism in implementation processes are more varied among the three countries.     

Dilemmas when working with substance abusers with multiple and complex problems: the case manager's perspective

Since the 1990s, case management has been implemented in the USA and Canada – and recently also in various European countries – to support substance abusers with multiple and complex needs. Although this intervention is often presented as a set of standardised functions, its application is often a subjective task involving various dilemmas, which may influence case management outcomes significantly. Based on a comparison of case managers' experiences in Denmark and Belgium, we focus on several core dilemmas in case management for substance abusers with complex problems. Case management practices vary from one project to the next and even within the same project. Such differences are apparently related to the way in which case managers approach dilemmas such as those existing between control versus self-determination, or between systematic versus ad-hoc planning. The conclusion is that it is vital to discuss these dilemmas during training courses and supervision meetings in order to ensure that the intended form of intervention is actually delivered on the ground.     

Organisationsaufstellung — ein neues Zauberinstrument in der Beratung?

Constellations are very in. The method was used as secret advice in the family therapy a few years ago. Now it is taking an important place in company consulting. Constellations promise support in change processes, staff decisions, strategic new organizations, mergers and acquisitions, successor finding, coaching or supervision. It seems like there is no problem which can not be resolved through constellations. This apparent unlimited possible usage of constellation tempts the ‘constellator’ to act more and more as a consultant in all the above mentioned areas. After a short introduction to the method this report questions in a theoretical constructive systems perspective, the universal competence of constellations and thus also of the ‘constellator’. It is furthermore investigated if the currently prevailing ways of using the method are able to discern the organization phenomenon as an emergent level of order. The study takes away the aura of constellation as a consulting instrument with the goal to demonstrate under which conditions the method can cope with the self-dynamics of organizations.