Suchergebnisse

AbstractAttempts have been made to identify factors influencing the sex ratio at birth (number of males per 100 females). Statistical analyses have shown that comparisons between sex ratios demand large data sets. The secondary sex ratio has been believed to vary inversely with the frequency of prenatal losses. This hypothesis suggests that the ratio is highest among singletons, medium among twins and lowest among triplets. Birth data in Sweden for the period 1869–2004 showed that among live births the secondary sex ratio was on average 105.9 among singletons, 103.2 among twins and 99.1 among triplets. The secondary sex ratio among stillbirths for both singletons and twins started at a high level, around 130, in the 1860s, but approached live birth values in the 1990s. This trend is associated with the decrease and convergence of stillbirth rates among males and females. For detailed studies, we considered data for Sweden in 1869–1878 and in 1901–1967. Marital status or place of residence (urban or rural) had no marked influence on the secondary sex ratio among twins. For triplets, the sex ratio showed large random fluctuations and was on average low. During the period 1901–1967, 20 quadruplet, two quintuplet and one sextuplet set were registered. The sex ratio was low, around 92.0.

AbstractIn national birth registers of Caucasians, the secondary sex ratio, that is, the number of boys per 100 girls at birth, is almost constant at 106. Variations other than random variation have been noted, and attention is being paid to identifying presumptive influential factors. Studies of the influence of different factors have, however, yielded meagre results. An effective means of identifying discrepancies is to investigate birth data compiled into sibships of different sizes. Assuming no inter- or intra-maternal variations, the distributions of the sex composition are binomial. Varying parental tendencies for a specific sex result in discrepancies from the binomial distribution. Over a century ago, the German scientists Geissler and Lommatzsch analyzed the vital statistics of Saxony, including twin maternities, for the last quarter of the 19th century. They considered sibships ending with twin sets. Their hypothesis was that in sibships ending with male–male twin pairs, the sex ratio among previous births is higher than normal, while in sibships with female–female twin pairs, the sex ratio is lower than normal. If the sibship ended with a male-female pair, then the sex ratio is almost normal. Consequently, a same-sex twin set indicated, in general, deviations in the sex ratio among the sibs within the sibship. Our analyzes of their data yielded statistically significant results that support their statements.

This article adopts a comparative perspective to review the recent increase in the sex ratio at birth (SRB) across Asia. It first describes and compares the most recent birth statistics in Asia in order to identify commonalities in the gradual rise of SRBs observed from Armenia to South Korea. This comparison provides the basis for identifying specific transition patterns in the changes in SRBs. Their recent rise is then interpreted in a social and historical framework borrowed from fertility decline and based on three preconditions: access to sex‐selection technology, preference for male births, and pressure from low fertility. On a broader plane, the process of growing imbalances in the sex composition of the population gives rise to a tragedy of the commons. This article indicates the factors that appear most likely to trigger a turnaround in this transitional demographic situation and to facilitate a return to biologically normal sex ratios in the future.

SummaryScientists commonly use world average data on sex ratio at birth for India for want of dependable ones. Here an attempt is made to redress the problem to some extent. It is shown that this ratio has been high in India since the 1950s. The ratio has been strikingly high, even prior to the time of inception of prenatal sex identification technologies. The ratio shows a rising trend due to several biological reasons. In addition, it has been rising sharply for a couple of decades due to some socio-medical factors. The natural sex ratio at birth in India is noticeably higher than the world average.

Abstract
Using data of 638 terrorist groups operating in 92 countries for the period 1970–2016, we examine the relationship between gender imbalance and a resident terrorist group survival. Our empirical design employs alternative models and controls for terrorist group characteristics, base-country influences, and unobservable regional fixed effects. An increase in male-to-female ratio is associated with lower probability of terrorist groups demise, suggesting that countries with a skewed male population are less able to combat terrorism.