Genetic algorithms for the analysis of Bayesian hierarchical partition models

Hierarchical partition models (see Malec and Sedransk, 1992, Consonni and Veronese, 1995) aim at finding an optimal grouping (partition) of a set of experiments regarding a target variable. In this class of models the partition is regarded as an unknown parameter, and one of the main goals is computing the posterior distribution over the class of the possible partitions. This problem has been addressed in Sampietro and Veronese (1998), where a Metropolis-Hastings algorithm is applied. In this paper the performance of an alternative procedure, based on the logic of genetic algorithms, is evaluated. The results of the two approaches are compared, even if a conjoint use of them is to be advised.     

“Birds of a Feather” Fail Together: Exploring the Nature of Dependency in SME Defaults

This article studies the effects of incorporating the interdependence among London small business defaults into a risk analysis framework using the data just before the financial crisis. We propose an extension from standard scoring models to take into account the spatial dimensions and the demographic characteristics of small and medium‐sized enterprises (SMEs), such as legal form, industry sector, and number of employees. We estimate spatial probit models using different distance matrices based only on the spatial location or on an interaction between spatial locations and demographic characteristics. We find that the interdependence or contagion component defined on spatial and demographic characteristics is significant and that it improves the ability to predict defaults of non–start‐ups in London. Furthermore, including contagion effects among SMEs alters the parameter estimates of risk determinants. The approach can be extended to other risk analysis applications where spatial risk may incorporate correlation based on other aspects.     

JEEA‐FBBVA LECTURE 2013: THE NEW EMPIRICAL ECONOMICS OF MANAGEMENT

Over the last decade the World Management Survey (WMS) has collected firm‐level management practices data across multiple sectors and countries. We developed the survey to try to explain the large and persistent total factor productivity (TFP) differences across firms and countries. This review paper discusses what has been learned empirically and theoretically from the WMS and other recent work on management practices. Our preliminary results suggest that about a quarter of cross‐country and within‐country TFP gaps can be accounted for by management practices. Management seems to matter both qualitatively and quantitatively for performance at the level of the firm and the nation. Competition, governance, human capital, and informational frictions help account for the variation in management. We make some suggestions for both policy and future research.     

Running on Empty: The Operating Reserves of U.S. Nonprofit Organizations

Operating reserves allow nonprofit organizations to smooth out imbalances between revenues and expenses, helping to maintain program output in the presence of fiscal shocks. We know surprisingly little about why nonprofits might save operating reserves and what factors explain variation between organizations' savings behavior. Findings suggest that operating reserves are reduced in the presence of concentrated public funds, access to debt, fixed assets, and endowment. However, size is not an important predictor, indicating that the lack of reserves is not limited to small nonprofit organizations but is instead a sectorwide issue. Significant numbers of nonprofits maintain no operating reserves at all. One potential explanation is that organizations discount the benefits of reserves because they are evaluated on spending, focusing instead on the “benefits of costs.” This preference for spending over reserving may also help explain the general lack of liquidity in the sector beyond operating reserves alone.     

Is the Partner Who Decides to Divorce More Attractive? A Comparison Between Initiators and Noninitiators

Five hundred eighty divorced individuals from Germany, Italy, and Switzerland provided retrospective reports on the perceived similarities and differences between themselves and their former partner and on their own and their partner's attractiveness. Initiators and noninitiators were compared with regard to these different variables. Results demonstrated that most divorcees perceived themselves to be quite similar to their former partner. Initiating women were more likely than noninitiating women to perceive themselves as different from their former partner in personality, norms, and needs and to evaluate their former partner to be less attractive. Initiating men were more likely than noninitiating men to perceive differences with regard to the personality between themselves and their partners.     

Couples Therapy for Intimate Partner Violence: A Systematic Review and Meta‐Analysis

Intimate partner violence is a serious public health problem accompanied by substantial morbidity and mortality. Despite its documented impact on health, there is no widely recognized treatment of choice. Some studies indicate that couples suffering from situational violence may benefit from couples therapy, but professionals are cautious to risk the possibility of violent retaliation between partners. After a comprehensive literature search of 1,733 citations, this systematic review and meta‐analysis compiles the results of six studies to investigate the effectiveness of couples therapy as a treatment for violence. Preliminary data suggest that couples therapy is a viable treatment in select situations.     

Equation reliability of soil ingestion estimates in mass-balance soil ingestion studies

Exposure to chemicals from ingestion of contaminated soil may be an important pathway with potential health consequences for children. A key parameter used in assessing this exposure is the quantity of soil ingested, with estimates based on four short longitudinal mass-balance soil ingestion studies among children. The estimates use trace elements in the soil with low bioavailability that are minimally present in food. Soil ingestion corresponds to the excess trace element amounts excreted, after subtracting trace element amounts ingested from food and medications, expressed as an equivalent quantity of soil. The short duration of mass-balance studies, different concentrations of trace elements in food and soil, and potential for trace elements to be ingested from other nonsoil, nonfood sources contribute to variability and bias in the estimates. We develop a stochastic model for a soil ingestion estimator based on a trace element that accounts for critical features of the mass-balance equation. Using results from four mass-balance soil ingestion studies, we estimate the accuracy of soil ingestion estimators for different trace elements, and identify subjects where the difference between Al and Si estimates is larger (>3 RMSE) than expected. Such large differences occur in fewer than 12% of subjects in each of the four studies. We recommend the use of such criteria to flag and exclude subjects from soil ingestion analyses.     

Daily Soil Ingestion Estimates for Children at a Superfund Site

Ingestion of contaminated soil by children may result in significant exposure to toxic substances at contaminated sites. Estimates of such exposure are based on extrapolation of short-term-exposure estimates to longer time periods. This article provides daily estimates of soil ingestion on 64 children between the ages of 1 and 4 residing at a Superfund site; these values are employed to estimate the distribution of 7-day average soil ingestion exposures (mean, 31 mg/day; median, 17 mg/day) at a contaminated site over different time periods. Best linear unbiased predictors of the 95th-percentile of soil ingestion over 7 days, 30 days, 90 days, and 365 days are 133 mg/day, 112 mg/day, 108 mg/day and 106 mg/day, respectively. Variance components estimates (excluding titanium and outliers, based on Tukey's far-out criteria) are given for soil ingestion between subjects (59 mg/day)2, between days on a subject (95 mg/day)2, and for uncertainty on a subject-day (132 mg/day)2. These results expand knowledge of potential exposure to contaminants among young children from soil ingestion at contaminated sites. They also provide basic distributions that serve as a starting point for use in Monte Carlo risk assessments.     

Exploring sequences: a graphical tool based on multi-dimensional scaling

Summary.  Sequence analysis has become one of the most used and discussed tools to describe life course trajectories. We introduce a new tool for the graphical exploratory analysis of sequences. Our plots combine standard sequence plots with the results that are provided by multi-dimensional scaling. We apply our procedure to describe work and family careers of Israeli women by using data from the Israel Social Mobility Survey. We first focus on some preliminary choices relative to the definition of the sequences: the age span, the length of the sequences and the set of states registered in each time period. We then describe how our plots can be used to gain insights about the main features of sequences and about the relationships between sequences and external information.