Zero variance Markov chain Monte Carlo for Bayesian estimators

Interest is in evaluating, by Markov chain Monte Carlo (MCMC) simulation, the expected value of a function with respect to a, possibly unnormalized, probability distribution. A general purpose variance reduction technique for the MCMC estimator, based on the zero-variance principle introduced in the physics literature, is proposed. Conditions for asymptotic unbiasedness of the zero-variance estimator are derived. A central limit theorem is also proved under regularity conditions. The potential of the idea is illustrated with real applications to probit, logit and GARCH Bayesian models. For all these models, a central limit theorem and unbiasedness for the zero-variance estimator are proved (see the supplementary material available on-line).     

A critical look at Lo's modified R/S statistic

We report on an empirical investigation of the modified rescaled adjusted range or R/S statistic that was proposed by Lo, 1991. Econometrica 59, 1279–1313, as a test for long-range dependence with good robustness properties under ‘extra’ short-range dependence. In contrast to the classical R/S statistic that uses the standard deviation S to normalize the rescaled range R, Lo's modified R/S-statistic V_q is normalized by a modified standard deviation S_q which takes into account the covariances of the first q lags, so as to discount the influence of the short-range dependence structure that might be present in the data. Depending on the value of the resulting test-statistic V_q, the null hypothesis of no long-range dependence is either rejected or accepted. By performing Monte-Carlo simulations with ‘truly’ long-range- and short-range dependent time series, we study the behavior of V_q, as a function of q, and uncover a number of serious drawbacks to using Lo's method in practice. For example, we show that as the truncation lag q increases, the test statistic V_q has a strong bias toward accepting the null hypothesis (i.e., no long-range dependence), even in ideal situations of ‘purely’ long-range dependent data.     

Is a loosely specified regulatory intervention effective in disciplining management commentary? The case of performance indicator disclosure

This paper offers a contribution to the call for research on the effectiveness of regulatory interventions governing management commentary disclosure. Specifically, we focus on the mandatory requirement concerning performance indicator disclosure introduced by the Modernisation Directive (2003/51/EC). In keeping with other regulators, the European legislator opted to implement a regulatory approach based on a rule with loose specifications. To understand the effects of this Directive, we have investigated the Italian context, in which neither the national legislator nor the standard setter have supported companies with detailed specifications or guidelines aimed at integrating the European provision. We have compared companies’ disclosure practices before and after the adoption of the Directive, investigating the number of disclosed indicators and also their modalities of presentation, as they are considered essential to guaranteeing the quality of this disclosure. Our results document that a mandatory intervention, even if based on loose specifications, is associated with an increase in disclosure practices. Nevertheless, such regulation does not seem able to guarantee high quality disclosure practices. In fact, before and after the regulation, companies primarily disclose common financial measures. Moreover, the usefulness of such disclosure is undermined by a limited compliance with the international guidelines concerning the modalities of presentation. These results reveal some weaknesses in the European approach to performance indicator regulation. In general, the EU legislator fails to explain the purpose and the objective of performance indicator disclosure and does not take into account the differences between financial and non-financial indicators. Furthermore, it does not provide firms with clear guidelines concerning the presentation modalities.     

Dual class shares,board of directors’ effectiveness and firm’s market value: an empirical study

This study aims to identify whether a relationship exists between the controlling shareholders’ voting power and outside directors’ effectiveness in maximizing firms’ financial performance. We analyze a panel data with 3057 observations for the 2000–2012 period using a random effects model, logit and probit regressions, and the two-stage model of Heckman in the Brazilian stock market. Our findings show that firms whose controlling shareholders use dual class shares to leverage their voting power have less independence from the board and worse financial performance and market value. Further, the percentage of outside directors tends to be ineffective in increasing the firm’s value, and in changing the firm’s chief executive officer (CEO) when (1) the controlling shareholder’s voting power is leveraged, or (2) when the CEO assumes a position on the board of directors simultaneously. We interpreted that these results are in line with the arguments in favor of the existence of a new agency cost, which is related to the undue obedience of board members to authority, such as the largest controlling shareholder or the CEO in Brazilian listed firms.     

Coaching von Unternehmern Erfahrungen und Wirkungen

Coaching of owner-entrepreneurs — experiences and effectsThe author argues that the kind of coaching which owner-entrepreneurs require differs in fundamental ways from the kind of coaching for hired top managers. The difference is rooted in the higher level of complexity of the decision problems of owner-entrepreneurs, which needs to be reflected in a more complex approach chosen by the coach. In this context, the ability to make himself better understood by others turns out to be a very essential key capacity which some owner-entrepreneurs lack and which a qualified coach can help them to regain.     

Benchmark Dose Analysis via Nonparametric Regression Modeling

Estimation of benchmark doses (BMDs) in quantitative risk assessment traditionally is based upon parametric dose‐response modeling. It is a well‐known concern, however, that if the chosen parametric model is uncertain and/or misspecified, inaccurate and possibly unsafe low‐dose inferences can result. We describe a nonparametric approach for estimating BMDs with quantal‐response data based on an isotonic regression method, and also study use of corresponding, nonparametric, bootstrap‐based confidence limits for the BMD. We explore the confidence limits’ small‐sample properties via a simulation study, and illustrate the calculations with an example from cancer risk assessment. It is seen that this nonparametric approach can provide a useful alternative for BMD estimation when faced with the problem of parametric model uncertainty.     

Determinanten des Informationsgehalts von Managementprognosen – eine empirische Untersuchung anhand der DAX und MDAX-Unternehmen

In this article the characteristics and determinants of the information content of management earnings forecasts of the German DAX and MDAX companies between 2002 and 2005 are analyzed. As proxy for the information content I use the precision of the wording of a forecast. I can show that the forecasts of MDAX companies are more precisely formulated than those of DAX companies. Furthermore forecasts are formulated more precisely, when companies have, (1) a lower percentage of intangible assets, (2) lower market capitalization, (3) lower volatility of earnings and (4) a higher need for external financing.     

Road socialism

Road socialists maintain that government is the best manager for the nation's vehicular transportation arteries. Contrary to their views, the present author maintains that the managerial role can best be fulfilled by private entrepreneurs. Under highway privatization, he claims, traffic fatalities and automobile congestion will be sharply reduced.The author wishes to thank the North American Editor of Transport Policy, and an anonymous referee from the present journal, for helpful suggestions and commentary on an earlier draft of this paper.     

Opportunity sets and individual well-being

 An opportunity set ranking rule assigns an ordering of opportunity sets to each individual utility function (defined on the universal set of alternatives) within the domain of this rule. Using an axiomatic approach, this paper characterizes a general class of opportunity set ranking rules which are based on the utilities associated with the elements of an opportunity set. It is argued that the addition of an alternative to a given opportunity set is not necessarily desirable in terms of overall well-being, and this position is reflected in replacing a commonly used monotonicity axiom with an alternative condition. Received: 15 May 1995/Accepted: 14 December 1995     

Pregnancy-related dropouts and gender inequality in education: A life-table approach and application to Cameroon

In this study, I used a life-table approach to estimate how much hypothetical reductions in pregnancy-related dropouts would help close the gender gap in educational attainment. Using the schooling histories of 6,686 pupils, I partitioned Cameroon's gender gap in education into "pregnancy-related" and "non-pregnancy-related" components and simulated the impact of reductions in pregnancy-related dropouts on this gap. The results suggest that such reductions would have substantial payoffs in this setting, but payoffs would be the greatest where societies also address gender inequities before puberty and outside the realm of pregnancy. Reductions in pregnancy-related dropouts complement but do not replace efforts to reduce gender discrimination in schooling. Recent data from Demographic and Health Surveys should make it possible to extend this analysis to other countries.