Everything You Always Wanted To Know About Sex (Selection)

Population recently embarked on a new annual series of articles providing an overview of emerging demographic issues spanning the latest research on data, theories, and policy implications. Prenatal sex selection — now spreading from Asia to Eastern Europe — has been selected as the topic for the first installment.

Sex selection – the various processes to choose the sex of the offspring - is a topic that fascinates the public, and everyone seems to have an opinion about the relative merits of a boy versus a girl, or the mysterious factors (from the observing the lunar cycle to following special diets) that may influence a child’s sex at conception. Although folk traditions across the world have long had their own secret recipes for beating the biological odds, the last fifty years have also provided a plethora of new technological advances for sex selection. With the help of tools provided by a booming healthcare industry, sex selection methods — from sex-selective abortions to pre-implantation genetic diagnosis — have been successfully implemented. Consequently, sex selection has moved beyond an anthropological and statistical curiosity to become an unexpected source of worldwide demographic imbalance. The joint impact of prenatal and postnatal sex selection over the last thirty is responsible for the majority male population observed in the world today.

Recent research has shown that sex imbalances at birth cause a range of estimation and computational challenges. To start with, the sex ratio at birth (male births per 100 female births) in China and India — two countries with the largest birth imbalances — are based on estimates provided by fragile data samples. The absence of reliable birth registration statistics has meant that in many countries basic indicators (such as the parity-based sex ratio at birth) remain unknown. As for prenatal diagnosis abortion — the main culprit of sex imbalances — we simply have no direct data about its frequency or the sex of the aborted foetuses. The long-term implications are also difficult to foresee. While we are able to forecast the impact of a high sex ratio at birth on future populations — as was recently done in the United Nations’ 2015 Population Prospects — it is far more complicated to estimate the number of females missing due to gender discrimination. Furthermore, the impact of sex imbalances on the marriage market is yet another area requiring innovative demographic two-sex models, alongside the need for some plausible sociological hypotheses about the ways in which social systems will adapt to the growing surplus of young adult males.

Demographers are often asked to predict the future of sex imbalances across the world, and if we are to rely exclusively on the data available for trends across Asian and European countries, we may advance a few observations.

Firstly, sex ratio at birth usually hovers around a “natural” level — a range from 103 in Sub-Saharan Africa, to 105 elsewhere. However, sex ratio at birth may rise abruptly — a trend seen in several countries following the collapse of the Soviet Union in 1991. Interestingly, a preference for a higher proportion of female births has never been observed and suggests a timeless preference for male over female births.

Secondly, male birth preference does not rise indefinitely and instead tends to level off after a decade or so of regular increase. The plateau may be reached at 110, as in Southeast Europe, or at 125, as in some Chinese and Indian regions. This situation represents a kind of provisional equilibrium between various factors: son preference, sex selection technology, and fertility levels.

Thirdly, an ultimate decline and return to normalcy in affected areas appears to be possible. For instance, the South Korean sex ratio at birth has now returned to 106, after peaking at 115 twenty years ago. Other regions in Asia and Eastern Europe have shown similar signs of a downturn. These features unmistakably remind us of the fertility decline that took many countries to levels well-below replacement, and then followed a rebound towards a higher, more sustainable fertility level.

Yet, to understand the future of sex imbalances we may wish to move beyond basic data-driven models and return to the fundamentals of gender bias. The basic theory that construes prenatal sex selection as the product of several factors — low fertility, son preference, and technological supply — offers a more reasonable hypotheses than a purely chartist approach based on past trends and raw data.

Figure 1 illustrates my own interpretation of sex ratio transitions across various countries. In a couple of regions with high pre-existing levels of son preference and a steady level of birth masculinity, a future rise in sex imbalance seems plausible. Several countries, such as Nigeria and Afghanistan, with lower fertility levels or a broader access to sex selection technologies, including abortion, may eventually express their latent and unmet need for prenatal sex selection.

On the contrary, where kinship systems are more balanced and more favourable to women, there is a lower risk of sex selection imbalance. The desire for children of a particular gender sometimes expressed by parents is unlikely to translate into active gender discrimination.

In countries currently affected by an excess of male births, birth masculinity seems bound to eventually decrease. This will not be due to a rise in fertility levels or the initiation of government policies that seek a decline in the use of sex selection technologies. Instead, son preference will eventually run out of steam. This may be increased by women’s empowerment that could make patriarchal systems obsolete, or that traditional family systems will eventually crumble under the pressure of a growing number of surplus men forced to remain single and, therefore unable to fulfil the “patriarchal contract” (i.e. marry and beget sons).

Whatever the case, millions of recently-born males will find themselves trapped in this protracted sex-structural transition during the next fifty years. In turn, the issue of sex imbalances will remain on demographers’ agendas longer than the challenges of AIDS or fertility decline.

Figure 1: An interpretation of sex ratio dynamics in various parts of the world in 2015


This entry was posted in Fertility, Gender, Youth by Christophe Z. Guilmoto. Bookmark the permalink.
Christophe Z. Guilmoto

About Christophe Z. Guilmoto

Christophe Z. Guilmoto is senior fellow in demography at the French Institut de recherche pour le développement. He works presently at CEPED and teaches at the Paris-Descartes University and at the Ecole des hautes études en sciences sociales in Paris. He is member of the Editorial Board of the journal Population. His recent work on sex imbalances has taken him to Southeast Europe and Caucasus, as well as to East, South and Southeast Asia. A book co-edited with Gavin Jones on the demography of China, India and Indonesia will be published this year by Springer.

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