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In recently developed hierarchical age-period-cohort (HAPC) models, inferential questions arise: How can one assess or judge the significance of estimates of individual cohort and period effects in such models? And how does one assess the overall statistical significance of the cohort and/or the period effects? Beyond statistical significance is the question of substantive significance. This paper addresses these questions. In the context of empirical applications of linear and generalized linear mixed-model specifications of HAPC models using data on verbal test scores and voter turnout in U.S. presidential elections, respectively, we describe a two-step approach and a set of guidelines for assessing statistical significance. The guidelines include assessments of patterns of effects and statistical tests both for the effects of individual cohorts and time periods as well as for entire sets of cohorts and periods. The empirical applications show strong evidence that trends in verbal test scores are primarily cohort driven, while voter turnout is primarily a period phenomenon. [ABSTRACT FROM PUBLISHER]

The article discusses the relationship between birth certificates and child labor laws in the U.S. from the 1870s through the 1930s, including efforts of labor reformers to have employers use age to regulate youth employment. An overview of parents' perspectives on their children's ages, including in regard to their lack of documentation of their children's birth dates, is provided. The role that the U.S. census played in maintaining records on age and birth dates is discussed.

The religiosity of scientists is a persistent topic of interest and debate among both popular and academic commentators. Researchers look to this population as a case study for understanding the intellectual tensions between religion and science and the possible secularizing effects of education. There is little systematic study, however, of religious belief and identity among academic scientists at elite institutions, leaving a lacuna of knowledge in this area. This absence of data exists at a time when the intersection between religion and science is reaching heightened public attention. Especially with increased tensions surrounding teaching evolution in the public schools, understanding what kind of resources scientists have (particularly in terms of their own religious beliefs and practices) to transmit science to a broader religiously-motivated public is crucial. Using data from a recent survey of academic scientists at twenty-one elite U.S. research universities, we compare the religious beliefs and practices of natural and social scientists within seven disciplines as well as academic scientists to the general population. We find that field-specific and interdisciplinary differences are not as significant in predicting religiosity as other research suggests. Instead, demographic factors such as age, marital status, and presence of children in the household are the strongest predictors of religious difference among scientists. In particular, religiosity in the home as a child is the most important predictor of present religiosity among this group of scientists. We discuss the relevance these findings have for understanding issues related to current theory and public debate about the intersection between religion and science. [ABSTRACT FROM AUTHOR]