Another look into the effect of premarital cohabitation on duration of marriage: an approach based on matching

Summary.  The paper proposes an alternative approach to studying the effect of premarital cohabitation on subsequent duration of marriage on the basis of a strong ignorability assumption . The approach is called propensity score matching and consists of computing survival functions conditional on a function of observed variables (the propensity score), thus eliminating any selection that is derived from these variables. In this way, it is possible to identify a time varying effect of cohabitation without making any assumption either regarding its shape or the functional form of covariate effects. The output of the matching method is the difference between the survival functions of treated and untreated individuals at each time point. Results show that the cohabitation effect on duration of marriage is indeed time varying, being close to zero for the first 2–3 years and rising considerably in the following years.     

Winding Stairs: A sampling tool to compute sensitivity indices

Sensitivity analysis aims to ascertain how each model input factor influences the variation in the model output. In performing global sensitivity analysis, we often encounter the problem of selecting the required number of runs in order to estimate the first order and/or the total indices accurately at a reasonable computational cost. The Winding Stairs sampling scheme (Jansen M.J.W., Rossing W.A.H., and Daamen R.A. 1994. In: Gasman J. and van Straten G. (Eds.), Predictability and Nonlinear Modelling in Natural Sciences and Economics. pp. 334–343.) is designed to provide an economic way to compute these indices. The main advantage of it is the multiple use of model evaluations, hence reducing the total number of model evaluations by more than half. The scheme is used in three simulation studies to compare its performance with the classic Sobol' LP. Results suggest that the Jansen Winding Stairs method provides better estimates of the Total Sensitivity Indices at small sample sizes.     

Balanced Asymmetrical Nearly Orthogonal Designs for first and second order effect estimation

A method for constructing asymmetrical (mixed-level) designs, satisfying the balancing and interaction estimability requirements with a number of runs as small as possible, is proposed in this paper. The method, based on a heuristic procedure, uses a new optimality criterion formulated here. The proposed method demonstrates efficiency in terms of searching time and optimality of the attained designs. A complete collection of such asymmetrical designs with two- and three-level factors is available. A technological application is also presented.     

Presenting Results from Model Based Studies to Decision-Makers: Can Sensitivity Analysis be a Defogging Agent?

The motivation of the present work is to provide an auxiliary tool for the decision-maker (DM) faced with predictive model uncertainty. The tool is especially suited for the allocation of R&Dresources. When taking decisions under uncertainties, making use of the output from mathematical or computational models, the DM might be helped if the uncertainty in model predictions be decomposed in a quantitative-rather than qualitativefashion, apportioning uncertainty according to source. This would allow optimal use of resources to reduce the imprecision in the prediction. For complex models, such a decomposition of the uncertainty into constituent elements could be impractical as such, due to the large number of parameters involved. If instead parameters could be grouped into logical subsets, then the analysis could be more useful, also because the decision maker might likely have different perceptions (and degrees of acceptance) for different kinds of uncertainty. For instance, the decomposition in groups could involve one subset of factors for each constituent module of the model; or one set for the weights, and one for the factors in a multicriteria analysis; or phenomenological parameters of the model vs. factors driving the model configuratiodstructure aggregation level, etc.); finally, one might imagine that a partition of the uncertainty could be sought between stochastic (or aleatory) and subjective (or epistemic) uncertainty. The present note shows how to compute rigorous decomposition of the output's variance with grouped parameters, and how this approach may be beneficial for the efficiency and transparency of the analysis.     

The Islamic Banking Industry in Jordan

Thirty-three years ago Islamic banking was considered wishful thinking. However, serious research over the past two-and-a-half decades has shown that Islamic banking is not only feasible and viable, but is an efficient and productive way of financial intermediation. A number of Islamic banks have also been established during this period in Jordan. The objective of this paper is to examine the structure and performance of the Islamic banking industry in Jordan during the period 2000–2006. We find that the Jordanian Islamic banking industry is still in its infancy compared to a number of countries in the region and there is a growth trend in the financial services market, despite its current concentration and limited size.     

A class of neutral to the right priors induced by superposition of beta processes

A random distribution function on the positive real line which belongs to the class of neutral to the right priors is defined. It corresponds to the superposition of independent beta processes at the cumulative hazard level. The definition is constructive and starts with a discrete time process with random probability masses obtained from suitably defined products of independent beta random variables. The continuous time version is derived as the corresponding infinitesimal weak limit and is described in terms of completely random measures. It takes the interpretation of the survival distribution resulting from independent competing failure times. We discuss prior specification and illustrate posterior inference on a real data example.     

A hierarchical modelling approach for measuring reliability of and agreement between two types of magnetic field dosimeter

Summary.  The paper describes how to use hierarchical models to assess the reliability of and agreement between two or more types of measurement device. The idea is illustrated by fitting a linear model with nested random effects to a set of data that was obtained from the calibration of two samples of extremely low frequency magnetic field meters. The paper focuses on the formulation of a suitable model that accounts for the various aspects of the calibration protocol and the subsequent interpretation of the parameter estimates. The approach is very flexible and can easily be tuned to the various needs arising in the measurement agreement framework. It can be seen as an extension of the common practice of using a one-way random-effects model to retrieve a measure of agreement.     

Economic growth,labour flexibilization and employment quality in Colombia, 2002–11

Over the period 2002–11, the Colombian labour market saw a marked improvement in employment opportunities, accompanied by an increase in nonstandard forms of employment. The authors look at how this affected employment quality, using a composite index based on Categorical Principal Components Analysis (CATPCA). They observe a small but widespread improvement in employment quality – mainly for self‐employed women – brought about by higher earnings, increased social protection and less time‐related underemployment. However, a considerable “quality deficit” remains, which calls for policies to strengthen labour market institutions and stimulate productivity and investment.     

Barriers and Enablers to Safeguarding Children and Adults within a Disability Services Context: Insights from an Australian Delphi Study

Research conducted in the 1990s revealed the tragic irony that exposure to the disability support system, and particularly to its institutional forms, was a major risk factor related to the neglect and abuse of children and adults with a disability. Subsequently, a range of policies have been introduced to minimize risk. However, recurring events of abuse and neglect in the disability services sector in high and middle income countries demonstrate that processes geared to safeguard children and adults with a disability from abuse and neglect remain insufficient. To establish the wider fabric of organizational factors that contribute to effective safeguarding practices within the Australian disability support sector, a modified online Delphi study was conducted, capturing the views of disability services staff and managers (n = 249) regarding barriers and enablers to effective safeguarding. This study identified issues concerning organizational culture, management practice, workforce development, client capacity building and contextual factors. During Round Two of the Delphi, participants were asked to rate the categorized enabler statements according to importance on a 10‐point Likert scale, to ascertain the degree of consensus. A total of 262 of the statements were regarded as important or very important. The Delphi result highlighted the considerable gap between the wider systemic and cultural processes that, in the eyes of disability services staff and management, contribute to good safeguarding practice and the safeguarding measures currently in place. The article calls for a holistic approach to safeguarding that addresses procedural issues and to the transformation of the wider systemic and cultural fabric of an organization.     

On the volume-ranking of opportunity sets in economic environments

We provide a characterization of the volume-ranking of opportunity sets as defined on the set of all polyconvex sets, i.e. finite unions of convex, compact, Euclidean sets. In fact, such a domain is large enough to encompass most of the opportunity sets typically encountered in economic environments, including non-linear or even non-convex budget sets, and opportunity sets arising from production sets. Our result relies on a valuation-based volume-characterization theorem due to Klain and Rota (Introduction to Geometric Probability, Cambridge University Press, Cambridge, 1997) and helps to highlight some quite unusual conditions under which the volume-ranking can be justified as a freedom-ranking of opportunity sets. Therefore, it may also help to understand why the latter has been so conspicuously ignored in welfare analysis. Thanks are due to Larry Kranich, Massimo Marinacci, Uri Rothblum, Ernesto Screpanti, John Weymark, Yongsheng Xu, Claudio Zoli and two anonymous referees for helpful comments and suggestions.