Modeling individual migraine severity with autoregressive ordered probit models

This paper considers the problem of modeling migraine severity assessments and their dependence on weather and time characteristics. We take on the viewpoint of a patient who is interested in an individual migraine management strategy. Since factors influencing migraine can differ between patients in number and magnitude, we show how a patient’s headache calendar reporting the severity measurements on an ordinal scale can be used to determine the dominating factors for this special patient. One also has to account for dependencies among the measurements. For this the autoregressive ordinal probit (AOP) model of Müller and Czado (J Comput Graph Stat 14: 320–338, 2005) is utilized and fitted to a single patient’s migraine data by a grouped move multigrid Monte Carlo (GM-MGMC) Gibbs sampler. Initially, covariates are selected using proportional odds models. Model fit and model comparison are discussed. A comparison with proportional odds specifications shows that the AOP models are preferred.     

Happy People Have Children: Choice and Self-Selection into Parenthood

There is mixed evidence in the existing literature on whether children are associated with greater subjective well-being, with the correlation depending on which countries and populations are considered. We here provide a systematic analysis of this question based on three different datasets: two cross-national and one national panel. We show that the association between children and subjective well-being is positive only in developed countries, and for those who become parents after the age of 30 and who have higher income. We also provide evidence of a positive selection into parenthood, whereby happier individuals are more likely to have children.     

Pair‐copula constructions for non‐Gaussian DAG models

We propose a new type of multivariate statistical model that permits non‐Gaussian distributions as well as the inclusion of conditional independence assumptions specified by a directed acyclic graph. These models feature a specific factorisation of the likelihood that is based on pair‐copula constructions and hence involves only univariate distributions and bivariate copulas, of which some may be conditional. We demonstrate maximum‐likelihood estimation of the parameters of such models and compare them to various competing models from the literature. A simulation study investigates the effects of model misspecification and highlights the need for non‐Gaussian conditional independence models. The proposed methods are finally applied to modeling financial return data. The Canadian Journal of Statistics 40: 86–109; 2012 © 2012 Statistical Society of Canada     

Initiating Senior Co-Housing: People,Place, andLong-Term Security

Abstract

An increasing proportion of older people are unable to afford rental or purchase of age-appropriate residential accommodation in Australia. This article reports on a community-initiated research project investigating feasibility of affordable co-housing for older residents wishing to age in their community. Factors enabling successful co-housing for seniors were investigated through a systematic literature review. The multiphase participatory research approach drew on the knowledge of local seniors, community support workers, and planning and design professionals through workshops and interviews in a regional community in southeast Queensland. The findings demonstrate interest in and barriers to senior co-housing. The research engagement approach enables tailored solutions for individual long-term security, relevant to small communities in Australia.     

Real estate and real estate finance as a research field—an international overview

We present a citation-based analysis of the most important journals on real estate and real estate finance over a time period from 1986 to 2010. For each year, those three articles with the highest number of citations according to Google Scholar are identified. A thorough analysis of all 75 selected articles reveals that the focus of interest has been on (1)empirical research, (2) mainly using data ofresidential real estate, with (3) the primary objective of evaluating real estateinvestment until the midst 1990s. In order to derive reliable risk-return relations for real estate investment, (4) asset pricing as the main task of real estateappraisal is in the centre of attention, too. Appraisal issues have relatively gained importance for the last fifteen years in comparison to investment issues. Interdisciplinary aspects and sustainable issues are only very rarely integrated in appraisal methods, the focus is primarily on maximizing economic returns. Therefore, our citation analysis confirms that the Financial Management Approach of Dasso and Woodward (1980) is the predominant approach particularly in the United States. Our findings regarding our basic sample of articles are cross-checked by several robustness tests. For future research activities, it seems to be quite promising to focus on the one hand on interdisciplinary aspects and on the other hand to contribute to the theoretical foundation of real estate with the aim of developing a common body of knowledge.     

Joint decisions on household membership and human capital accumulation of youths. The role of expected earnings and local markets

This paper analyses the effects of expected earnings and local markets conditions on the behaviour of young adults with high school diplomas. Decisions to either remain in the parental home or form a new household are modelled jointly with those of either gaining work experience or investing in a university education. Expected lifetime earnings are found to play a crucial role in determining the choice of studying and residing with parents. Poor labour market opportunities discourage young people from working and induce them to study. The cost of housing greatly influences the choice of working and leaving the parental home. Received: 23 March 2001/Accepted: 26 November 2001 All correspondence to Gianna Claudia Giannelli. Helpful comments by two anonymous referees are gratefully acknowledged. Responsible editor: John F. Ermisch.     

Point‐of‐Use Hybrid Inventory Policy for Hospitals

Modern point‐of‐use technology at hospitals has enabled new replenishment policies for medical supplies. One of these new policies, which we call the hybrid policy, is currently in use at a large U.S. Midwest hospital. The hybrid policy combines a low‐cost periodic replenishment epoch with a high‐cost continuous replenishment option to avoid costly stockouts. We study this new hybrid policy under deterministic and stochastic demand. We develop a parameter search engine using simulation to optimize the long‐run average cost per unit time and, via a computational study, we provide insights on the benefits (reduction in cost, inventory, and number of replenishments) that hospitals may obtain by using the hybrid policy instead of the commonly used periodic policies. We also use the optimal hybrid policy parameters from the deterministic analysis to propose approximate expressions for the stochastic hybrid policy parameters that can be easily used by hospital management.      

Retailer Transshipment versus Central Depot Allocation for Supply Network Design

We consider a supply chain structure with shipments from an external warehouse directly to retailers and compare two enhancement options: costly transshipment among retailers after demand has been realized vs. cost‐free allocation to the retailers from the development of a centralized depot. Stochastic programming models are developed for both the transshipment and allocation structures. We study the impact of cost parameters and demand coefficient of variation on both system structures. Our results show an increasing convex relationship between average costs and demand coefficient of variation, and furthermore that this increase is more pronounced for the allocation structure. We employ simulation and nonlinear search techniques to computationally compare the cost performance of allocation and transshipment structures under a wide range of system parameters such as demand uncertainty and correlation; lead times from the external warehouse to retailers, from warehouse to central depot, and from depot to retailers; and transshipment, holding, and penalty costs. The transshipment approach is found to outperform allocation for a broad range of parameter inputs including many situations for which transshipment is not an economically sound decision for a single period. The insights provided enable the manager to choose whether to invest in reducing lead times or demand uncertainty and assist in the selection of investments across identical and nonidentical retailers.     

Estimating and comparing adverse event probabilities in the presence of varying follow-up times and competing events

Safety analyses of adverse events (AEs) are important in assessing benefit–risk of therapies but are often rather simplistic compared to efficacy analyses. AE probabilities are typically estimated by incidence proportions, sometimes incidence densities or Kaplan–Meier estimation are proposed. These analyses either do not account for censoring, rely on a too restrictive parametric model, or ignore competing events. With the non-parametric Aalen-Johansen estimator as the “gold standard”, that is, reference estimator, potential sources of bias are investigated in an example from oncology and in simulations, for both one-sample and two-sample scenarios. The Aalen-Johansen estimator serves as a reference, because it is the proper non-parametric generalization of the Kaplan–Meier estimator to multiple outcomes. Because of potential large variances at the end of follow-up, comparisons also consider further quantiles of the observed times. To date, consequences for safety comparisons have hardly been investigated, the impact of using different estimators for group comparisons being unclear. For example, the ratio of two both underestimating or overestimating estimators may not be comparable to the ratio of the reference, and our investigation also considers the ratio of AE probabilities. We find that ignoring competing events is more of a problem than falsely assuming constant hazards by the use of the incidence density and that the choice of the AE probability estimator is crucial for group comparisons.     

DOING IT WHEN OTHERS DO: A STRATEGIC MODEL OF PROCRASTINATION

This paper develops a strategic model of procrastination in which present‐biased agents prefer to perform an onerous task with someone else. This turns their decision of when to perform the task into a procrastination game—a dynamic coordination game between present‐biased players. The model characterizes the conditions under which interaction mitigates or exacerbates procrastination. A procrastinator matched with a worse procrastinator may perform her task earlier than she otherwise would: she wants to avoid the increased temptation that her peer's company would generate. Procrastinators can thus use bad company as a commitment device to mitigate their self‐control problem. (JEL C72, C73, D03, D91)