Selection (genetic and cultural) and environmental variation are the principal mechanisms determining patterns of demographic change in human populations. Conditions exist under which the nature and intensity of these forces can be inferred from temporal trends in the demographic variables. These conditions, which can be expressed in terms of relations between the Malthusian parameter and popul...

Environmental factors influence the dynamics and regulation of biological populations through their influences on demographic variables, but demographic mechanisms of population regulation have received little attention. We investigated the demographic basis of regulation of Columbian ground squirrel (Spermophilus columbianus) populations under natural and experimentally food-supplemented condi...

background: there have been speculations about the effects of hormonal changes and socio-demographic factors on periodontal health during pregnancy.objective: according to the lack of sufficient epidemiologic information about the periodontal status of pregnant women in yazd, this study was accomplished to determine the changes of community periodontal index for treatment needs (cpitn) during p...

"This paper steps back from the current political debate [in the United States] over the social security trust fund and examines the more general question of how serious a macroeconomic problem aging is and how policy should respond to it. We focus primarily on issues relating to saving and capital accumulation. We do not consider the broader question of whether the current U.S. national savi...

Causes of cyclic fluctuations in abundance (population cycles) of some small-mammal populations remain poorly understood despite 6 decades of research and .20 hypotheses. Population cycles are demographic processes and cannot be fully explained without considering demographic mechanisms that underlie cyclic fluctuations in abundance. From simulation studies, we have recently shown that phase-re...

"The aim of this paper is to analyze empirically the causal relationship, if any, between infant mortality and fertility in thirty-five developing countries." The focus is on possible relationships between the infant mortality rate and the fertility rate. "The hypothesis that infant mortality causes fertility is tested. The possibility of a 'reverse causation' is also analyzed. A one-sided ...

Different family compositions and sizes may affect child development through the different modes of interaction between family members. Previous studies have compared only children with non-only children in cognitive/non-cognitive outcomes. However, relatively little research has systematically investigated the potential moderators among them. Using a large and representative sample of Chinese ...