Bayesian analysis of mixture modelling using the multivariate t distribution

A finite mixture model using the multivariate t distribution has been shown as a robust extension of normal mixtures. In this paper, we present a Bayesian approach for inference about parameters of t-mixture models. The specifications of prior distributions are weakly informative to avoid causing nonintegrable posterior distributions. We present two efficient EM-type algorithms for computing the joint posterior mode with the observed data and an incomplete future vector as the sample. Markov chain Monte Carlo sampling schemes are also developed to obtain the target posterior distribution of parameters. The advantages of Bayesian approach over the maximum likelihood method are demonstrated via a set of real data.     

Creating a reference to a complex emergency situation using time series methods: war in Guinea-Bissau 1998-1999

Impacts of complex emergencies or relief interventions have often been evaluated by absolute mortality compared to international standardized mortality rates. A better evaluation would be to compare with local baseline mortality of the affected populations. A projection of population-based survival data into time of emergency or intervention based on information from before the emergency may create a local baseline reference. We find a log-transformed Gaussian time series model where standard errors of the estimated rates are included in the variance to have the best forecasting capacity. However, if time-at-risk during the forecasted period is known then forecasting might be done using a Poisson time series model with overdispersion. Whatever, the standard error of the estimated rates must be included in the variance of the model either in an additive form in a Gaussian model or in a multiplicative form by overdispersion in a Poisson model. Data on which the forecasting is based must be modelled carefully concerning not only calendar-time trends but also periods with excessive frequency of events (epidemics) and seasonal variations to eliminate residual autocorrelation and to make a proper reference for comparison, reflecting changes over time during the emergency. Hence, when modelled properly it is possible to predict a reference to an emergency-affected population based on local conditions. We predicted childhood mortality during the war in Guinea-Bissau 1998-1999. We found an increased mortality in the first half-year of the war and a mortality corresponding to the expected one in the last half-year of the war.     

Effects of Medicaid managed care policies on mental health service use among a national probability sample of children in the child welfare system

Children in the child welfare system are dependent upon Medicaid to finance services for their considerable mental health needs. This study examines the effects of Medicaid policies on mental health service use among a national probability sample of children in the child welfare system. Data for this study came from the National Survey of Child and Adolescent Well-Being, the Caring for Children in Child Welfare study, and the Area Resource File. Weighted multivariate logistic regression analyses were conducted to estimate effects of policy variables on children's use of mental health services, controlling for child-level covariates and county-level health resources. Children in counties with behavioral carve-outs under Medicaid managed care had lower odds of inpatient mental health service use. Medicaid managed care enrollment and variations in type of provider reimbursement did not affect use of mental health services. Older age, greater need for mental health services, and higher levels of caregiver education were associated with increased odds of service use. Restrictions on use of inpatient mental healthcare caused by behavioral carve-outs may disproportionately affect children in the child welfare system who have high rates of such use. Careful adoption of carve-outs is necessary to assure appropriate care for these children.     

Social identities and political cleavages: the role of political context

Summary. Using a novel method, the paper investigates the influence of social group identities on attitudes and on voting in a variety of political contexts. Examining the major regions of Britain, Canada and the USA, we find considerable national and regional diversity in the nature of social cleavages. For example, social class and race had widely different effects across societies, but within societies their effects on attitudes and on voting were very similar. However, despite that, age and religion had a similar effect on attitudes across societies; the effects on voting varied considerably. The significant within-country differences underline the importance of using region, rather than country, as the unit of analysis. More importantly, these results highlight the role of political context, especially competing cleavages and the structure of party competition, in the establishment of politically relevant social cleavages.     

In search of rigor, relevance, and legitimacy: what drives the impact of publications?

In this study, we introduce the concept of legitimacy to the rigor-relevance debate and investigate empirically how rigor, relevance, and legitimacy are related to the process of knowledge dissemination within a research field. We argue that this analysis has been a missing piece in the debate on rigor and relevance when institutional logics about what constitutes both elements lead researchers to act according to what they perceive to be appropriate behavior in the research field. We draw on insights from the micro and macro levels of institutional theory to show how researchers aiming to bestow legitimacy on their own work conform to these “rules of the game”. Using meta-analytical techniques, we focus on the field of strategic entrepreneurship and analyze how rigor- and relevance-related characteristics of studies in this field are linked to their legitimacy and therefore to the impact they have in the research community.     

The Gender Gap in Orgasms: Survey Data from a Mid-Sized Canadian City

Objective: Previous research has established a gap in orgasm frequency between men and women. This study investigates explanations for the gender gap in orgasm. Methods: Crosstab analysis and logistic regression are used to examine the gender gap in orgasms from one Canadian city: Hamilton, Ontario (N = 194). Results: We find a strong association between women’s orgasms and the type of sexual behavior in which partners engage. Women who receive oral sex are more likely to reach orgasm. Conclusion: Sexual practices focused on clitoral stimulation are important to reducing the gender gap in orgasms.     

SOCIAL BACKGROUND,EDUCATION, AND INEQUALITY

The role parents' education plays for the educational achievements of children is a source of unequal opportunities. Through this channel the number of educated affects the options of future cohorts, creating a social multiplier effect making improvements in education self‐reinforcing. Policies to compensate for inequalities of opportunities—public education or transfers—have very different implications. Transfers not only reduce inequality on impact but also reduce social mobility, while public education—even if a perfect substitute to private education—works in the opposite direction. Social impediments to education are similar to a market imperfection, and publicly provided education may lead to a Pareto improvement. (JEL D3, I2, H2, H4)     

DOES THE PUBLIC SECTOR IMPLODE FROM BAUMOL'S COST DISEASE?

The root of the Baumol cost disease is higher productivity increases for manufactured goods than for services. The implied increase in relative costs of service production is widely claimed to have devastating implications for the public sector as a provider of tax‐financed services such as health, education, and care. To match the increasing costs it appears inevitable that tax rates would be ever increasing. It is shown that this inference does not follow under standard assumptions when accounting explicitly for service provision from both the private and public sectors. Strikingly under assumptions often made in the literature, the welfare maximizing tax rate for a utilitarian policy maker would remain constant despite the Baumol cost disease, and by implication the share of public employment in total employment will remain constant. (JEL H5, H11, O41)     

Research-in-Progress Sessions Create a More Inclusive and Engaging Regional Conference

The Pacific Sociological Association annual meeting recently added a new session type called the Research-in-Progress (RIP) session. The purpose of adding these sessions was to provide an opportunity for attendees to present research still in formative stages of completion in order to get useful feedback. Presentations ranged from doctoral dissertation proposals to nearly completed research. Early experience from RIP session organizers and discussants is that these sessions were lively and engaging, sparking a great deal of audience participation. Feedback from presenters indicated that they received useful feedback. Based on our initial experience with the RIP sessions, we believe they are a beneficial addition to the meetings.