A reply to Avery and Hakkert

Udry et al., ¹ J. Richard Udry, Charles Teddlie and C. M. Suchindran, ‘The Random Variation in Rates Based on Total Enumeration of Events’, Population Studies, d33, 2, (1979), pp. 353-364. while analysing the variations in observed birth rates, found that the usual binomial model variance underestimates the actual variance of birth rates. Avery and Hakkert's ² Avery, R. C. and Hakkert, R., Comment on ‘The Random Variation in Rates Based on Total Enumeration of Events’ by Udry, Teddlie and Suchindran. analysis offers some help in interpreting these results. Also, it clarifies one possible explanation given by Udry et al., regarding the heterogeneous populations. However, we show below that the narrow approach taken by Avery and Hakkert is difficult to apply to general situations and perhaps leads them to make a number of inappropriate statements.     

Statistical modeling of selected aspects of the childbearing process with application to world fertility survey countries∗

The childbearing process should be monitored in developing countries experiencing high population growth rates and high levels of maternal and infant mortality. A mathematical model for estimation of certain aspects of the childbearing process, which requires only data on age‐specific fertility rates, is developed. Synthetic maternal childbearing indices, namely, mean ages at first and last birth, length of reproductive life span, inter‐birth spacing, and proportion of childless women, in addition to the well‐known mean age at childbearing, for the WFS countries are obtained using the proposed model. The indices are free from age truncation effects, and, under certain assumptions, provide information about a cohort's completed fertility before the women stop reproducing. The effects of women's residence and education on fertility are also examined.     

Intergenerational Profiles of Socioeconomic (Dis)advantage and Obesity During the Transition to Adulthood

Investigations of socioeconomic status (SES) and health during the transition to adulthood in the United States are complicated by the later and more varied transitions in residence, employment, schooling, and social roles compared with previous generations. Parental SES is an important influence during adolescence but cannot sufficiently capture the SES of the independent young adult. Typical, single SES indicators based on income or education likely misclassify the SES of young adults who have not yet completed their education or other training, or who have entered the labor force early with ultimately lower status attainment. We use a latent class analysis (LCA) framework to characterize five intergenerational SES groups, combining multidimensional SES information from two time points—that is, adolescent (parental) and young adult (self) SES data. Associations of these groups with obesity, a high-risk health outcome in young adults, revealed nuanced relationships not seen using traditional intergenerational SES measures. In males, for example, a middle-class upbringing in adolescence and continued material advantage into adulthood was associated with nearly as high obesity as a working poor upbringing and early, detrimental transitions. This intergenerational typology of early SES exposure facilitates understanding of SES and health during young adulthood.     

The effects of children on divorce and re-marriage: a multivariate analysis of life table probabilities

Summary Using proportional hazards models and multiple decrement life tables to analyse data from the 1973 National Survey of Family Growth, this study tests the hypotheses that, net of the effects of such factors as age at separation or divorce, the probabilities of divorce after separation and of re-marriage after divorce would be lower for women with larger numbers of children or younger children, and that these transitions would take longer than for women with fewer or older children or women who were childless; and that there would be an interaction between number of children and age of youngest child. Results included: (1) the probability that mothers of two or more children would divorce after separation was significantly lower than for childless women, or those with only one child; (2) among whites, mothers of three or more children were at a significant disadvantage regarding their chances of re-marriage, whereas the probability that a black mother of three or more children would re-marry was no smaller than that of a woman with fewer or no children; (3) among whites, the presence of a youngest child aged between two and five years at separation decreased the probability of divorce after separation; (4) there was no interaction effect between number and age of children; and (5) in each category of family size and age of youngest child, the probability that a black woman would divorce after separation or re-marry after divorce was lower than for white women. The results have important implications for the study of divorce and re-marriage, and for understanding of problems of single-parent families.     

Estimates of fecundability from a truncated distribution of conception times

A population consisting of women who have conceived before a time t ignores all women whose conception time exceeds t. Such a population is considered as a truncated population, and the samples are called truncated samples. Under the assumption that fecundability among women varies according to a Beta distribution (with parameters a and b), the distribution of conception times in a truncated population can be considered as truncated Type I geometric. This paper presents an algorithm to obtain the moment and maximum likelihood estimates of a and b from the truncated samples. Large sample properties of the estimators are also studied. Examples using the Hutterite and the Princeton Fertility Survey data are given.     

Detecting nuclear materials smuggling: performance evaluation of container inspection policies

In recent years, the United States, along with many other countries, has significantly increased its detection and defense mechanisms against terrorist attacks. A potential attack with a nuclear weapon, using nuclear materials smuggled into the country, has been identified as a particularly grave threat. The system for detecting illicit nuclear materials that is currently in place at U.S. ports of entry relies heavily on passive radiation detectors and a risk-scoring approach using the automated targeting system (ATS). In this article we analyze this existing inspection system and demonstrate its performance for several smuggling scenarios. We provide evidence that the current inspection system is inherently incapable of reliably detecting sophisticated smuggling attempts that use small quantities of well-shielded nuclear material. To counter the weaknesses of the current ATS-based inspection system, we propose two new inspection systems: the hardness control system (HCS) and the hybrid inspection system (HYB). The HCS uses radiography information to classify incoming containers based on their cargo content into "hard" or "soft" containers, which then go through different inspection treatment. The HYB combines the radiography information with the intelligence information from the ATS. We compare and contrast the relative performance of these two new inspection systems with the existing ATS-based system. Our studies indicate that the HCS and HYB policies outperform the ATS-based policy for a wide range of realistic smuggling scenarios. We also examine the impact of changes in adversary behavior on the new inspection systems and find that they effectively preclude strategic gaming behavior of the adversary.     

The Development of Four Types of Adolescent Dating Abuse and Selected Demographic Correlates

This study determined the shape of trajectories from ages 13 to 19 of 4 types of dating abuse perpetration and examined whether the demographic characteristics of sex, minority status, socioeconomic status, and family structure systematically explained variation in the trajectories. The data are from 5 waves of data collected from 973 adolescents participating in the control group of a randomized trial. The mean trajectory for psychological dating abuse was positive linear, but the mean trajectories were curvilinear for moderate physical, severe physical, and sexual dating abuse. At all ages, boys reported more severe physical and sexual dating abuse than girls, minorities reported more moderate and severe physical dating abuse than Whites, adolescents in single‐parent households reported more psychological and severe physical dating abuse than those in 2‐parent‐households, and parental education was negatively associated with psychological and moderate physical dating abuse perpetration. The findings have implications for future research and for practice.     

Childbearing and family in remarriage

Proportional hazards models are used to test hypotheses about the effect of women’s prior childbearing on the probability of having a birth in remarriage and to analyze the effects of other factors. Results indicate that the number of children at the time of remarriage has no effect on childbearing probabilities, but the age of the youngest child has a significant effect. These findings support the view that having a child is important to confirm the marriage, but that individual and family life course factors also affect the decision to have a child in a remarriage.