COHORT

Cohorts are people sharing a similar experience or event at a particular time. For example all children born in a particular place and time, or all students graduating from high school in a particular place and time are cohorts. Cohorts are frequently used in longitudinal research. Marvin Wolfgang, for example, established a research project to follow all male children born in Philadelphia in 1940 in order to determine their encounters with the police.

Identification of Parameters in Cohort Models - WOLFGANG JAGODZINSKI, University of Köln, Sociological Methods & Research, Vol. 12, No. 4, 375-398 (1984) - Linear-additive age-period cohort models that permit the maximum number of aging effects, period effects, and cohort effects (full cohort models) are underidentified. In this article, some general rules will be given for detecting identified and underidentified parameters in any full cohort model under zero-sum restrictions.

It will be demonstrated that only one parameter in a dimension is identified whenever the number of parameters in this dimension is uneven. Otherwise, no parameter is identified. Full cohort models for larger tables contain more overidentifying restrictions, but the number of identified parameters never exceeds four.

Cleavage and Ideological Voting in Age Cohorts - van der Brug, Wouter.
Abstract: This study compares the effects of religion, social class and left-right on party choice between EU countries, over 15 years and between generations. Generational replacement leads to a decreasing effect of long-term determinants of the vote.

Advances in Age–Period–Cohort Analysis - Herbert L. Smith, University of Pennsylvania, Philadelphia, Sociological Methods & Research, Vol. 36, No. 3, 287-296 (2008).
The patterns of rates by age at one point in time may not reflect the effects associated with aging, which are more properly studied in cohorts. Cohort succession, aging, and period-specific historical events provide accounts of social and demographic change. Cohort models can now be understood in a larger context. Age–period–cohort modeling call attention to the multilevel nature of the problem and draw on advances in methods, fixed and random effects, and identification in structural or causal models.

Secondary sex ratios and male lifespan: Damaged or culled cohorts
Ralph Catalano and Tim Bruckner, School of Public Health, University of California.
Controversy remains as to whether abortions result from reduced maternal tolerance of males at the low end of a relatively constant distribution of survivability, the “culled cohort” explanation, or from shifts in the whole distribution of survivability, the “damaged cohort” explanation. These alternatives make opposing predictions regarding the relationship between the secondary sex ratio and lifespan of male birth cohorts. Our results support the culled cohort argument.

Three-year incidence of AIDS in five cohorts of HTLV-III-infected risk group members
JJ Goedert, RJ Biggar, SH Weiss, ME Eyster, M Melbye, S Wilson, HM Ginzburg, RJ Grossman, RA DiGioia, WC Sanchez.
This long latency could account for the significantly higher AIDS incidence in the New York cohort compared with other cohorts if the virus entered the New York before it entered the populations from which the other cohorts were drawn.

GenomEUtwin Scientific Meeting. European Network of Twin Registries and MORGAM Cohorts. - Istituto Superiore di Sanità. Rome, 13-14 December 2004.
The project has developed and applied to twin and MORGAM cohorts new molecular technologies and statistical strategies to define and characterise the genetic, environmental and life-style risk factors of obesity, migraine, coronary heart disease and stroke.

Hospital Readmission Rates for Cohorts of Medicare Beneficiaries in Boston and New Haven - Elliott S. Fisher, John E. Wennberg, Therese A. Stukel, and Sandra M. Sharp.
The relative rate of readmission in Boston as compared with New Haven was 1.64 (95 percent confidence interval, 1.53 to 1.76) for all cohorts combined.