A multistate approach for estimating the incidence of human immunodeficiency virus by using data from a prevalent cohort study

Summary.  Cohort studies of individuals infected with the human immunodeficiency virus (HIV) provide useful information on the past pattern of HIV diagnoses, progression of the disease and use of antiretroviral therapy. We propose a new method for using individual data from an open prevalent cohort study to estimate the incidence of HIV, by jointly modelling the HIV diagnosis, the inclusion in the cohort and the progression of the disease in a Markov model framework. The estimation procedure involves the construction of a likelihood function which takes into account the probability of observing the total number of subjects who are enrolled in the cohort and the probabilities of passage through the stages of disease for each observed subject conditionally on being included in the cohort. The estimator of the HIV infection rate is defined as the function which maximizes a penalized likelihood, and the solution of this maximization problem is approximated on a basis of cubic M -splines. The method is illustrated by using cohort data from a hospital-based surveillance system of HIV infection in Aquitaine, a region of south-western France. A simulation study is performed to study the ability of the model to reconstruct the incidence of HIV from prevalent cohort data.     

Incorporating quality into data envelopment analysis of nursing home performance: A case study

When using data envelopment analysis (DEA) as a benchmarking technique for nursing homes, it is essential to include measures of the quality of care. We survey applications where quality has been incorporated into DEA models and consider the concerns that arise when the results show that quality measures have been effectively ignored. Three modeling techniques are identified that address these concerns. Each of these techniques requires some input from management as to the proper emphasis to be placed on the quality aspect of performance. We report the results of a case study in which we apply these techniques to a DEA model of nursing home performance. We examine in depth not only the resulting efficiency scores, but also the benchmark sets and the weights given to the input and output measures. We find that two of the techniques are effective in insuring that DEA results discriminate between high and low quality performance.     

MULTIVARIATE DECOMPOSITION FOR HAZARD RATE MODELS

We develop a regression decomposition technique for hazard rate models, where the difference in observed rates is decomposed into components attributable to group differences in characteristics and group differences in effects. The baseline hazard is specified using a piecewise constant exponential model, which leads to convenient estimation based on a Poisson regression model fit to person-period, or split-episode data. This specification allows for a flexible representation of the baseline hazard and provides a straightforward way to introduce time-varying covariates and time-varying effects. We provide computational details underlying the method and apply the technique to the decomposition of the black-white difference in first premarital birth rates into components reflecting characteristics and effect contributions of several predictors, as well as the effect contribution attributable to race differences in the baseline hazard .     

Sick building syndrome and perceived indoor environmental quality: A survey of apartment buildings in Hong Kong

The outbreak of a highly communicable disease, SARS, in Asia in 2003 has revealed the health risk of living in a high-density environment. To show the important connection between human health and environmental quality, this study surveys the prevalence of sick building syndrome (SBS) among apartment residents and their evaluation of indoor environmental quality (IEQ). Based on a sample of 748 households living in Hong Kong, two interesting findings are revealed: (1) nasal discomfort was the commonest home-related SBS symptom despite the absence of any central ventilation system in apartment buildings; (2) noise, rather than ventilation, was the major IEQ problem perceived by residents. Our statistical analysis further showed that residents with SBS symptoms were less satisfied with their IEQ than those without. That is, despite a positive evaluation of specific IEQ criteria with respect to the building residents lived in, if they reported feeling SBS related symptoms, the overall IEQ evaluation of their building could still be negative. This perception bias gives rise to a sample selection problem in measuring perceived IEQ, which has implications on housing management practices and the formulation of a healthy housing policy.     

Immediate and Longer-Term Connections Between Support and Stress in Pregnant/Parenting and Non-Pregnant/Non-Parenting Adolescents

Despite the substantial amount of literature focusing on social support for pregnant and parenting adolescents, few studies have directly examined the relationships among stress and social support across their transition to parenting. The present study investigates the nature of the relationship between stress and support both before and after the birth of the baby. Two groups of adolescent females (one group facing parenthood and one not) completed measures of support and stress across a 7-month period (N = 231) to coincide with the transition to parenthood. In general, support and stress were negatively related when measured concurrently and positively related over time for parenting adolescents but not the non-parenting group. Understanding how long social support impacts stress will enable practitioners to identify when best to provide interventions for pregnant and parenting adolescents.     

Do taboo trade-offs explain the difficulty in valuing health and social interventions?

Persistent anomalies in the results of willingness to pay studies, despite improvements in measurement technique, challenge the assumption in economics that all sources of value are commensurable. Two sources of incommensurability have been identified: interdimensional incommensurability, which refers to the cognitive difficulty that people encounter when trying to assign a monetary value to health; and constitutive incommensurability, which arises when some forms of trade-off are regarded as ‘taboo’. In this paper we explore whether the notion of taboo trade-offs might explain some of the difficulties experienced in health-related willingness to pay studies.     

Cultural filtering in the hiring process and its relationship to welfare reform

In this paper, we perform an initial, exploratory analysis to determine whether firms use “cultural filters” as indirect and direct proxies for human capital when screening potential applicants for employment opportunities. Using data collected from three counties in Washington State, we find that these filters do, indeed, influence hiring decisions. As a result, it may be advantageous for policy makers to consider restructuring welfare policies to account for the effects of these cultural filters.     

实验经济学的兴起、发展及其在中国的应用前景

实验经济学是过去三十年中经济学发展最快的分支领域之一,近年来,田野实验的快速发展进一步加快了经济学的实验化进程。可以说,经济学家已经越来越依赖于实验来理解和解释经济现象与行为。不过这一状态来之不易。实验经济学一直是在驳斥与怀疑之中成长的,直到现在,围绕实验经济学的方法论而展开的争论也还在继续。本次访谈邀请了当前国际实验经济学的领军人物丹尼 尔.豪瑟（Daniel Houser）教授和在方法论上造诣颇深的罗卫东教授就实验经济学方法上的一些关键问题进行阐述,内容涉及实验经济学为什么会兴起并获得发展,实验室实验所面临的人工性、外部有效性方面的质疑,实验室实验、田野实验以及自然实验之间的关系,行为经济学和实验经济学之间的关系等核心问题,两位教授还对未来实验经济学在中国的发展提出了建设性意见。     

Mapping Invasive Species Risks with Stochastic Models: A Cross-Border United States-Canada Application for Sirex noctilio Fabricius

Nonindigenous species have caused significant impacts to North American forests despite past and present international phytosanitary efforts. Though broadly acknowledged, the risks of pest invasions are difficult to quantify as they involve interactions between many factors that operate across a range of spatial and temporal scales: the transmission of invading organisms via various pathways, their spread and establishment in new environments. Our study presents a stochastic simulation approach to quantify these risks and associated uncertainties through time in a unified fashion. We outline this approach with an example of a forest pest recently detected in North America, Sirex noctilio Fabricius. We simulate new potential entries of S. noctilio as a stochastic process, based on recent volumes of marine shipments of commodities from countries where S. noctilio is established, as well as the broad dynamics of foreign marine imports. The results are then linked with a spatial model that simulates the spread of S. noctilio within the geographical distribution of its hosts (pines) while incorporating existing knowledge about its behavior in North American landscapes. Through replications, this approach yields a spatial representation of S. noctilio risks and uncertainties in a single integrated product. The approach should also be appealing to decisionmakers, since it accounts for projected flows of commodities that may serve as conduits for pest entry. Our 30-year forecasts indicate high establishment probability in Ontario, Quebec, and the northeastern United States, but further southward expansion of S. noctilio is uncertain, ultimately depending on the impact of recent international treatment standards for wood packing materials.