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Cohort Size (cohort + size)

Distribution by Scientific Domains
Humanities and Social Sciences66%

Selected Abstracts

Stages of the Demographic Transition from a Child's Perspective: Family Size, Cohort Size, and Children's Resources

POPULATION AND DEVELOPMENT REVIEW, Issue 2 2008
David Lam
This article provides a new characterization of stages of the demographic transition from the perspective of children competing for resources within families and cohorts. In Stage 1 falling mortality increases the size of both families and birth cohorts. In Stage 2 falling fertility overtakes falling mortality to reduce family size, but population momentum causes continued growth in cohort size. In Stage 3 falling fertility overtakes population momentum to produce declining cohort size. We apply our framework to census microdata for eight countries and to United Nations population projections for a larger set of countries. The results suggest that most countries spend two to three decades in Stage 2, with declining family size offset by increasing cohort size. From the perspective of children aged 9,11, many countries enter Stage 3 between 2000 and 2010. Other countries, especially in Africa, will continue to experience increasing cohort size for several more decades. [source]

Relative Cohort Size: Source of a Unifying Theory of Global Fertility Transition?

POPULATION AND DEVELOPMENT REVIEW, Issue 2 2000
Diane J. Macunovich
Using United Nations estimates of age structure and vital rates for 184 countries at five-year intervals from 1950 through 1995, this article demonstrates how changes in relative cohort size appear to have affected patterns of fertility across countries since 1950,not just in developed countries, but perhaps even more importantly in developing countries as they pass through the demographic transition. The increase in relative cohort size (defined as the proportion of males aged 15,24 relative to males aged 25,59), which occurs as a result of declining mortality rates among infants, children, and young adults during the demographic transition, appears to act as the mechanism that determines when the fertility portion of the transition begins. As hypothesized by Richard Easterlin, the increasing proportion of young adults generates a downward pressure on young men's relative wages (or on the size of landhold-ings passed on from parent to child), which in turn causes young adults to accept a tradeoff between family size and material wellbeing, setting in motion a "cascade" or "snowball" effect in which total fertility rates tumble as social norms regarding acceptable family sizes begin to change. [source]

Nonmarital Fertility and the Effects of Divorce Rates on Youth Suicide Rates

JOURNAL OF MARRIAGE AND FAMILY, Issue 4 2006
Steven F. Messner
Using pooled, time-series data for a sample of 15 developed nations, we assess the effect of divorce rates on gender-specific suicide rates for youths aged 15 , 19 with models of relative cohort size, lagged nonmarital fertility, and an interaction term for divorce rates and nonmarital fertility. The results reveal that, for young men, relative cohort size is positively related to suicide rates, and divorce rates interact with lagged nonmarital fertility. The interaction effect indicates that increases in divorces are especially consequential for suicide cohorts of male youths who were born in periods of high nonmarital fertility. For female youths, only divorce rates exert a significant effect on suicide rates, and it is a positive, main effect. [source]

On the natural course of oral lichen lesions in a Swedish population-based sample

JOURNAL OF ORAL PATHOLOGY & MEDICINE, Issue 5 2006
A. Roosaar
Objectives:, The aim was to assess the natural course of oral lichen lesions (OLL) among unselected, non-consulting individuals. Subjects and methods:, A cohort of 327 subjects with OLL, confirmed in 1973,1974 during a population-based survey in two Swedish municipalities, was followed through January 2002 via record linkages with nationwide and essentially complete registers. A sample of 80 drawn from the 194 surviving subjects who still resided in the area in 1993,1995 was invited for interview and oral re-examination. Results:, At the end of follow-up, one case of oral cancer was detected, while 0.4 were expected. The overall mortality among subjects with OLL was not significantly different from that in the 15 817 OLL-free subjects who participated in the initial population based survey in 1973,1974. The lesion had disappeared in 14 (39%) of 36 re-examined subjects with white OLLs in 1973,1974, and four (11%) had transformed into red types. In the corresponding group of 19 with red forms initially, five (26%) had become lesion free and four (21%) had switched to white types. Although the cohort size does not permit firm conclusions regarding oral cancer risk, the natural course over up to 30 years appears to be benign in the great majority. [source]

Stages of the Demographic Transition from a Child's Perspective: Family Size, Cohort Size, and Children's Resources

POPULATION AND DEVELOPMENT REVIEW, Issue 2 2008
David Lam
This article provides a new characterization of stages of the demographic transition from the perspective of children competing for resources within families and cohorts. In Stage 1 falling mortality increases the size of both families and birth cohorts. In Stage 2 falling fertility overtakes falling mortality to reduce family size, but population momentum causes continued growth in cohort size. In Stage 3 falling fertility overtakes population momentum to produce declining cohort size. We apply our framework to census microdata for eight countries and to United Nations population projections for a larger set of countries. The results suggest that most countries spend two to three decades in Stage 2, with declining family size offset by increasing cohort size. From the perspective of children aged 9,11, many countries enter Stage 3 between 2000 and 2010. Other countries, especially in Africa, will continue to experience increasing cohort size for several more decades. [source]

Relative Cohort Size: Source of a Unifying Theory of Global Fertility Transition?

POPULATION AND DEVELOPMENT REVIEW, Issue 2 2000
Diane J. Macunovich
Using United Nations estimates of age structure and vital rates for 184 countries at five-year intervals from 1950 through 1995, this article demonstrates how changes in relative cohort size appear to have affected patterns of fertility across countries since 1950,not just in developed countries, but perhaps even more importantly in developing countries as they pass through the demographic transition. The increase in relative cohort size (defined as the proportion of males aged 15,24 relative to males aged 25,59), which occurs as a result of declining mortality rates among infants, children, and young adults during the demographic transition, appears to act as the mechanism that determines when the fertility portion of the transition begins. As hypothesized by Richard Easterlin, the increasing proportion of young adults generates a downward pressure on young men's relative wages (or on the size of landhold-ings passed on from parent to child), which in turn causes young adults to accept a tradeoff between family size and material wellbeing, setting in motion a "cascade" or "snowball" effect in which total fertility rates tumble as social norms regarding acceptable family sizes begin to change. [source]

Paternity and social rank in wild chimpanzees (Pan troglodytes) from the Budongo Forest, Uganda

AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 3 2010
Nicholas E. Newton-Fisher
Abstract We analyzed patterns of paternity and male dominance rank in the Sonso community of wild East African chimpanzees (Pan troglodytes schweinfurthii) in the Budongo Forest, Uganda. Our major objective was to determine whether and how social rank influenced paternity success. We successfully genotyped 52 individuals at up to nine microsatellite loci, using DNA extracted from fecal samples. Of 24 offspring analyzed, we identified sires for 21. Paternity success was significantly correlated with social rank, with alpha males siring a disproportionate number of offspring. However, both middle- and low-ranking males also fathered offspring, and the priority-of-access model provided a relatively poor prediction of which males would be successful and under what circumstances. The concentration of paternities among only seven males and the tendency for high-ranking males to sire offspring of multiparous females suggest that both individual variation in male quality and the resource value of particular females may be mediating factors. In comparison with other chimpanzee studies, our results support the hypothesis that larger male cohort size reduces the ability of the alpha male to monopolize females, though within our study, male number did not affect the success of the alpha. Successful sires were not necessarily those who achieved the highest mating success with the females whose offspring they sired, but were those who demonstrated higher investment by spending significantly more time in association with these females. Finally, we estimate extra-group paternity at 0,5%, supporting other evidence that the community serves as the primary reproductive unit in chimpanzees. Am J Phys Anthropol 2010. © 2009 Wiley-Liss, Inc. [source]

Utility-Based Optimization of Combination Therapy Using Ordinal Toxicity and Efficacy in Phase I/II Trials

BIOMETRICS, Issue 2 2010
Nadine Houede
Summary An outcome-adaptive Bayesian design is proposed for choosing the optimal dose pair of a chemotherapeutic agent and a biological agent used in combination in a phase I/II clinical trial. Patient outcome is characterized as a vector of two ordinal variables accounting for toxicity and treatment efficacy. A generalization of the Aranda-Ordaz model (1981,,Biometrika,68, 357,363) is used for the marginal outcome probabilities as functions of a dose pair, and a Gaussian copula is assumed to obtain joint distributions. Numerical utilities of all elementary patient outcomes, allowing the possibility that efficacy is inevaluable due to severe toxicity, are obtained using an elicitation method aimed to establish consensus among the physicians planning the trial. For each successive patient cohort, a dose pair is chosen to maximize the posterior mean utility. The method is illustrated by a trial in bladder cancer, including simulation studies of the method's sensitivity to prior parameters, the numerical utilities, correlation between the outcomes, sample size, cohort size, and starting dose pair. [source]