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41.
The main problem in applying the mean-variance portfolio selection consists of the fact that the first
two moments of the asset returns are unknown. In practice the optimal portfolio weights have to be estimated.
This is usually done by replacing the moments by the classical unbiased sample estimators. We provide a comparison
of the exact and the asymptotic distributions of the estimated portfolio weights as well as a sensitivity
analysis to shifts in the moments of the asset returns. Furthermore we consider several types of shrinkage
estimators for the moments. The corresponding estimators of the portfolio weights are compared with each
other and with the portfolio weights based on the sample estimators of the moments. We show how the uncertainty
about the portfolio weights can be introduced into the performance measurement of trading strategies. The
methodology explains the bad out-of-sample performance of the classical Markowitz procedures. 相似文献
42.
In this article, we present and explain a bio-psycho-social model of successful aging with subjective well-being as a criterion
of a successful aging process. We focus on physical activity because it is a crucial behavior. Physical activity can support
successful aging in two different ways: first, due to its physiological and cognitive effects, and Second, an older person
can enhance subjective well-being (SWB) while being physically active. The model points out that an older person can regulate
SWB. To do this, an older person should set and pursue personally and culturally valued goals. The strength of the association
between setting a goal and goal pursuance, respectively, and SWB depends on the extent a person is able to satisfy psychological
needs (autonomy, competence, relatedness). But, the decision as to which goal will be set and pursued does not belong to the
older person exclusively. The bio-psycho-social model explains that the chance to enhance SWB is restricted by personal dispositions
(e.g., physiological constitution, psychological factors) and social–structural constraints (e.g., predominant stereotype
of aging, facilities especially for target groups).
Funding credit: Landesstiftung Baden Württemberg gGmbH [Landesstiftung Foundation] 相似文献
43.
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In this paper, the focus is on sequential analysis of multivariate financial time series with heavy tails. The mean vector and the covariance matrix of multivariate non linear models are simultaneously monitored by modifying conventional control charts to identify structural changes in the data. The considered target process is a constant conditional correlation model (cf. Bollerslev, 1990), an extended constant conditional correlation model (cf. He and Teräsvirta, 2004), a dynamic conditional correlation model (cf. Engle, 2002), or a generalized dynamic conditional correlation model (cf. Capiello et al., 2006). For statistical surveillance we use control charts based on residuals. Further, the procedures are constructed for t-distribution. The detection speed of these charts is compared via Monte Carlo simulation. In the empirical study, the procedure with the best performance is applied to log-returns of the stock market indices FTSE and CAC. 相似文献
46.
Wolfgang Ludwig‐Mayerhofer Olaf Behrend Ariadne Sondermann 《Social Policy & Administration》2014,48(5):594-612
This article fills a gap in the existing literature by investigating how public employment service (PES) staff actually deal with their clients under a continental regime of activation. The results reported here are based on interviews both with PES staff and their unemployed clients in Germany. We argue that due to its Bismarckian origins as an insurance‐based system of ‘unemployment protection’, Germany's system of unemployment compensation is attractive not only for the marginalized, but also for core workers. As a result, PES staff deal with clients from very heterogeneous class backgrounds. We demonstrate that social class is a significant factor in client outcomes, and that earlier research has perhaps overemphasized the role of frontline staff as ‘street‐level bureaucrats’. While staff do have considerable power, the result of the encounters between the administration and clients also depends on the capabilities of the clients, which, in turn, are strongly related to social class. 相似文献
47.
Andrea Maurer Peter Imbusch Dirk Baier Klaus Boehnke Manuela Pötschke Henning Best Annette von Alemann Birgit Riegraf Corinna Onnen-Isemann Juliane Achatz Peter H. Hartmann Nicole Burzan Markus Klein Jens Aderhold Gerd Nollmann Arnold Wilts Mike Steffen Schäfer Christoph Görg Alexandra Manzei Christian Stegbauer Horst Pöttker Günter Endruweit Heiner Meulemann Heinz Sahner Erhard Stölting Wolfgang Lauterbach 《KZfSS K?lner Zeitschrift für Soziologie und Sozialpsychologie》2006,58(2):364-406
48.
Robert O. Hansson Margaret S. Stroebe and Wolfgang Stroebe 《The Journal of social issues》1988,44(3):207-216
A number of important themes and controversies emerged from the preceding papers. These include (a) what kinds of losses lead to grief; (b) how long grief lasts; (c) how to conceptualize "recovery," (d) the nature of "normal" grief; (e) whether bereavement has lasting effects on health; and (f) what characteristics of the individual, the relationship, or the nature of the death create a greater risk for poor outcome of bereavement. Consideration of these issues should help develop more effective strategies for intervention with sufferers, and social policies sensitive to the needs of those at greatest risk. 相似文献
49.
Protfolio optimization is very sensitive to the forecats of returns and (co-)variances of the underlying assets. This paper
applies a Bayesian vector-autoregression of the asset universe to predict the returns. Further, the co-variance matrix is
forecasted by an Augmented GARCH estimation of the most volatile principle components of the return series. As an empirical
illustration, the daily stock returns of the German stocks index DAX have been used to calculate some well-known mean-variance
portfolios. Back-testing is used to evaluate the performance. The approach seems to be promising. 相似文献
50.