Fertility

About: Fertility is a research topic. Over the lifetime, 29988 publications have been published within this topic receiving 681106 citations.

How the West 'Invented' Fertility Restriction ⁄

Abstract: Europeans restricted their fertility long before other parts of the world did so. By raising the marriage age of women, and ensuring that a substantial proportion remained celibate, the "European Marriage Pattern" (EMP) reduced childbirths by up to 40%. We analyze the rise of this first socio-economic institution in history that limited fertility through delayed marriage. Our model emphasizes changes in agricultural production following the Black Death. The production of meat, wool, and dairy (pastoral products) increased, while grain production declined. Women had a comparative advantage producing pastoral goods. They often worked as servants in husbandry, where they remained unmarried long after they had left the parental household. In a Malthusian world, this translated into lower population pressure, raising average wages by up to a quarter. The Black Death thus set into motion a virtuous circle of higher wages and fertility decline that underpinned Europe’s high per capita incomes. We demonstrate the importance of this effect in a calibration of our model.

Education and the Derived Demand for Children

Abstract: A negative correlation across households between parent's education and completed fertility is one of the most widely and frequently observed relationships in the empirical literature on human fertility behavior. In this paper I utilize the emerging economic theory of household behavior, which is also employed in other papers in this Supplement, to formulate an explanation for this observed negative correlation. In particular, the paper has two objectives: (1) to consider the mechanisms through which a couple's level of education might affect their fertility and (2) to document the effects of education on one of these mechanisms that is an aspect of fertility control-the choice of a contraceptive technique. The following section briefly outlines the theoretical framework, and in Section III I discuss the mechanisms through which education's influence may operate. Throughout, the discussion is restricted to channels of influence from education to fertility; that is, the reverse causation is ruled out by assumption. The specific focus of this discussion should not be interpreted as an assertion of the exclusiveness or the primacy of education's influence on fertility. Section IV considers the fertility-control decision in greater detail. It also reports on my initial empirical work with the 1965 National Fertility Study, a nationwide sociological survey of 5,600 U.S. women undertaken by the Office of Population Research at

The High Fertility of College Educated Women in Norway: An Artefact of the Separate Modelling of Each Parity Transition

Abstract: College education has a positive impact on birth rates, net of age and duration since previous birth, according to models estimated separately for second and third births. There are also indications of such effects on first-birth rates, in the upper 20s and 30s. Whereas a high fertility among the better-educated perhaps could be explained by socioeconomic or ideational factors, it might just as well be a result of selection. When all three parity transitions are modelled jointly, with a common unobserved factor included, negative effects of educational level appear. On the whole, the effects are less clearly negative for women born in the 1950s than for those born in the 1940s or late 1930s. The cohorts from the 1950s show educational differentials in completed fertility that are quite small and to a large extent stem from a higher proportion of childlessness among the better-educated. Second-birth progression ratios are just as high for the college educated as for women with only compulsory education, and the third-birth progression ratios differ very little. This reflects weakly negative net effects of education after first birth and spill-over effects from the higher age at first birth, counterbalanced by differential selectivity of earlier parity transitions.

Sperm mobility: mechanisms of fertilizing efficiency, genetic variation and phenotypic relationship with male status in the domestic fowl, Gallus gallus domesticus

Abstract: When females are sexually promiscuous, sexual selection continues after insemination through sperm competition and cryptic female choice, and male traits conveying an advantage in competitive fertilization are selected for. Although individual male and ejaculate traits are known to influence paternity in a competitive scenario, multiple mechanisms co-occur and interact to determine paternity. The way in which different traits interact with each other and the mechanisms through which their heritability is maintained despite selection remain unresolved. In the promiscuous fowl, paternity is determined by the number of sperm inseminated into a female, which is mediated by male social dominance, and by the quality of the sperm inseminated, measured as sperm mobility. Here we show that: (i) the number of sperm inseminated determines how many sperm reach the female sperm-storage sites, and that sperm mobility mediates the fertilizing efficiency of inseminated sperm, mainly by determining the rate at which sperm are released from the female storage sites, (ii) like social status, sperm mobility is heritable, and (iii) subdominant males are significantly more likely to have higher sperm mobility than dominant males. This study indicates that although the functions of social status and sperm mobility are highly interdependent, the lack of phenotypic integration of these traits may maintain the variability of male fitness and heritability of fertilizing efficiency.