The number of births varies markedly by season, but the causes of this variation are not well understood. The proposed explanations include temperature or photoperiod (affecting hormonal concentrations, sperm quality or sexual activity), seasonal variation in pregnancy loss, or cultural factors. In this paper we examined whether birth seasonality is influenced by socio-demographic factors. We used data on all live births registered in the Czech Republic in 1989-1991 (n = 387 496). Differences in the degree of seasonality between socio-demographic groups (defined by maternal age, marital status, education and birth order) were examined by inspection of curves, by comparing coefficients of variations of monthly numbers of births, and by calculating the ratios of the number of births in the 3 peak months (March to May) to the number of births in the 3 lowest months (October to December). We found large differences in the size of the seasonal variation in births by socio-demographic factors. The seasonal variation was highly pronounced in mothers who were 25-34 years old, had higher education, were married, and were pregnant with their second or third child. By contrast, birth seasonality was weak in mothers who were < or =19 years or > or =35 years old, unmarried, had low education, and expected their first or fourth or higher order birth. In a multivariate model, all four socio-demographic variables contributed significantly to seasonal variation. These results suggest that the seasonality of births is, at least in this population, strongly influenced by socio-demographic factors.

Scholars and policy makers have for centuries constructed and used developmental hierarchies to characterize different countries. The hypotheses motivating this paper are that such social constructions have been circulated internationally, are constructed similarly in various countries, and follow the social constructions of elite international organizations, such as the United Nations. This paper uses data from fifteen surveys in thirteen diverse countries to study how developmental hierarchies are understood in everyday life. Our research shows that most people have constructions of developmental hierarchies that are similar across countries and are similar to the developmental hierarchies constructed by the United Nations. These findings suggest that developmental hierarchies are widely understood around the world and are widely available to ordinary people as they make decisions about many aspects of life.

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Recent trends in German life expectancy show a considerable increase. Most of this increase has resulted from decreasing mortality at older ages. Patterns of oldest old mortality (ages 80+) differed significantly between men and women as well as between East and West Germany. While West German oldest old mortality decreased since the mid 1970s, comparable decreases in East Germany did not become evident until the late 1980s. Yet, the East German mortality decline accelerated after German reunification in 1990, particularly among East German females, attesting to the plasticity of human life expectancy and the importance of late life events. Medical care, individual economic resources and life-style factors are discussed as potential determinants of the decline in old age mortality in Germany.

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