A Diagnostic for Association in Bivariate Survival Models

We propose exploratory, easily implemented methods for diagnosing the appropriateness of an underlying copula model for bivariate failure time data, allowing censoring in either or both failure times. It is found that the proposed approach effectively distinguishes gamma from positive stable copula models when the sample is moderately large or the association is strong. Data from the Womens Health and Aging Study (WHAS, Guralnik et al., The Womenss Health and Aging Study: Health and Social Characterisitics of Older Women with Disability. National Institute on Aging: Bethesda, Mayland, 1995) are analyzed to demonstrate the proposed diagnostic methodology. The positive stable model gives a better overall fit to these data than the gamma frailty model, but it tends to underestimate association at the later time points. The finding is consistent with recent theory differentiating catastrophic from progressive disability onset in older adults. The proposed methods supply an interpretable quantity for copula diagnosis. We hope that they will usefully inform practitioners as to the reasonableness of their modeling choices.     

Pair Chart Test for an Early Survival Difference

The log-rank test is commonly used in comparing survival distributions between treatment and control groups in clinical trials. However, in many studies, the treatment is only effective at the early stage of the trial. Especially when the two survival curves cross, the log-rank test has a low statistical power to show the survival difference. We propose a test statistic for detecting such an early difference between the two treatment arms. The new test has an intuitive geometric interpretation based on a pair chart and is shown to have more power than the log-rank test when the treatment effect only appears in the early phase of the study. This advantage is evaluated for finite sample sizes in simulation studies. Finally, the proposed method is illustrated with a real data example of patients with gastric cancer.     

Accelerated Degradation Models for Failure Based on Geometric Brownian Motion and Gamma Processes

Based on a generalized cumulative damage approach with a stochastic process describing degradation, new accelerated life test models are presented in which both observed failures and degradation measures can be considered for parametric inference of system lifetime. Incorporating an accelerated test variable, we provide several new accelerated degradation models for failure based on the geometric Brownian motion or gamma process. It is shown that in most cases, our models for failure can be approximated closely by accelerated test versions of Birnbaum–Saunders and inverse Gaussian distributions. Estimation of model parameters and a model selection procedure are discussed, and two illustrative examples using real data for carbon-film resistors and fatigue crack size are presented.     

An Estimator of the Survival Function Basedon the Semi-Markov Model Under Dependent Censorship

Lee and Wolfe (Biometrics vol. 54 pp. 1176–1178, 1998) proposed the two-stage sampling design for testing the assumption of independent censoring, which involves further follow-up of a subset of lost-to-follow-up censored subjects. They also proposed an adjusted estimator for the survivor function for a proportional hazards model under the dependent censoring model. In this paper, a new estimator for the survivor function is proposed for the semi-Markov model under the dependent censorship on the basis of the two-stage sampling data. The consistency and the asymptotic distribution of the proposed estimator are derived. The estimation procedure is illustrated with an example of lung cancer clinical trial and simulation results are reported of the mean squared errors of estimators under a proportional hazards and two different nonproportional hazards models.     

Loss Averse Behavior

A behavioral condition of loss aversion is proposed and tested. Forty-nine students participated in experiments on binary choices among lotteries involving small scale real gains and losses. At the aggregate level, a significant proportion of the choices are in the direction predicted by loss aversion. Individuals can be classified as loss averse (28 participants), gain seeking (12), and unclassified (9). A comparison with risk behavior for binary choices on lotteries involving only gains shows that risk attitudes vary across these domains of lotteries. A gender effect is also observed: proportionally more women are loss averse. In contrast to the predictions of comonotonic independence, the size of common outcomes has systematic influence on choice behavior. JEL Classification: D81, C91     

Informational Asymmetries and Observational Learning in Search

As economics modeling moves from super rational decision makers to considering boundedly rational agents, some economic problems deserve a second look. This paper studies the effects of learning on the efficiency of search. Once learning is taken into account, the structure of information flow becomes important. In particular, I highlight the truncated information structure in the search problem. Agents stop searching once a sufficiently attractive price is found. Therefore, they observe the performance of shorter searches, but do not directly observe the performance of longer searches. I design and conduct an experiment to test the hypothesis that this asymmetric flow of information leads agents to search too little. I find strong evidence in its favor. This suggests that in the presence of learning, the provision of a more symmetric information structure will make search more efficient.JEL Classification: C91, D83     

The Multifaceted Impact of Education on Entry into Motherhood

This article studies the composite effect of education on young women’s entry into motherhood, using longitudinal data from Norway from 1971 to 2001. In line with previous research, we find that school enrolment delays motherhood, but having finished education there is a catching-up effect, as women who have completed at higher levels have their first child sooner than women who have completed at lower levels. Contrasting behaviour between women within various fields of education further indicate a career-adjustment effect related to differences in opportunity costs and/or preference heterogeneity. Finally, increasing educational differences in the timing of motherhood among younger cohorts suggest that long parental leaves and generous family benefits may fit better with a career track in some jobs than others.Lappegård T. et Rønsen M., 2005, The multifaceted impact of education on entry into motherhood, European Journal of Population 21: 31–49Lappegård T. et Rønsen M., 2005, Les multiples facettes de l’effet de l’instruction sur la maternité, Revue Européenne de Démographie, 21: 31–49     

Recessions and Mortality in Spain, 1980–1997

The relationship between economic fluctuations and mortality is assessed with data from Spain during the years 1980–1997, when national unemployment oscillated between 7% and 24%. Mortality rates of the Spanish provinces are modeled in fixed-effect panel regressions as functions of the demographic structure and the economic conditions. Unemployment effects on general mortality, sex-specific mortality, and mortality for major causes of death are negative, i.e., death rates increase procyclically when joblessness diminishes in an economic expansion. Homicides and female suicides are only weakly related or unrelated to economic fluctuations, but male suicides escalate countercyclically during economic downturns. Tapia Granados, J.A., 2005, Récession et mortalitéen Espagne, 1980–1997, Revue Européenne de Démographie, 21: 393–422.     

Patterns of Nonverbal Behavior and Sensivity in the Context of Attachment Relations

Nonverbal behavior and sensitivity to a relationship partner’s nonverbal behavior importantly influence the quality of interpersonal interactions and relationships, including attachment relationships. The abilities to encode, or express, and to decode, or understand, nonverbal cues are crucial to effective communication of emotions and are associated with social adjustment and relationship satisfaction. One important social context for the development and use of nonverbal encodingand decoding abilities is what Bowlby (1969/1982, Attachment and loss: Vol.1.Attachment (2nd ed.). New York: Basic Books) called attachment relationships—interpersonal relationships in which one person’s emotional security depends on another person’s sensitive, responsive caregiving and support. In this paper, we present theoretical ideas, review relevant research, and propose new avenues of research dealing with associations between attachment-related processes and patterns of nonverbal behavior and sensitivity in adulthood, two domains of research that have not previously been adequately connected.     

Cultural Discourse in Action: Interactional Dynamics and Symbolic Meaning

Cultural sociology has recently developed new tools with which to understand and analyze meaning in terms of cultural discourse. Specifically, this paper further develops the Alexanderian form of discourse analysis through application on the micro-level. Utilizing extensive ethnographic data, the mythopoetic men's movement is examined in terms of how its participants construct political meaning that motivates and guides their action. In empirical detail, these actors can be seen as creating a cultural discourse that constitutes the social movement at a fundamental level while at the same time the discourse is continually negotiated, contested, and reconfigured. Exposed is the “discourse of liberational masculinity” which is used by movement participants to challenge and confront hegemonic masculinity in American society. Examining the mythopoetic men's movement from this perspective demonstrates the analytic utility of this approach through revealing in unique ways the dynamics of morality, political belief, and perceived hegemony within this popular contemporary social movement.