Gender Ratio - Our World in Data

I'm interested in this study, from of trend standpoint: how has the gender ratio shifted? What is the cause of this shift? How does the present makeup effect society, politics, and economics. 

https://ourworldindata.org/gender-ratios

The ratio between the number of males and females in a society is referred to as the gender ratio. This ratio is not stable but instead shaped by biological, social, technological, cultural, and economic forces. And in turn the gender ratio itself has an impact on society, demography, and the economy.

In this entry we provide an overview of the variation and the changes of the gender ratio across the world. We study how it changes from birth to late life; the forces that change the ratio of men to women.

Many argue persuasively that the terms 'gender' and 'sex' are not to be used interchangeable.1

In this context here we have however decided to make an exception: we speak of the 'gender ratio' because it's the established term and it will help all those who want to be informed about this topic and search this term. But we also speak of the 'sex ratio' because this is arguably the more accurate term and it is increasingly used within the academic literature.

Summary

• The sex ratio at birth is not equal: in every country births are male-biased. There are biological reasons why there are slightly more boys born every year than girls. The 'natural' sex ratio at birth is around 105 boys per 100 girls (ranging from around 103 to 107 boys).
• In some countries, the sex ratio at birth is much more skewed than would occur naturally. Today and in the recent past this is particularly common across Asia and North Africa. Here there is clear evidence of gender selection through prenatal sex determination and selective abortion.
• In countries where there is a clear son preference, the sex ratio at birth becomes increasingly skewed with birth order (the third or fourth born children are more likely to be boys than the first or second child).
• In nearly every country, boys are more likely to die in childhood than girls. There are biological reasons for this: boys are more susceptible to birth complications and infectious diseases.
• In countries where there is strong son preference, mortality rates for girls are higher than would be expected: this can occur either through direct infanticide, but also through neglect and unequal treatment.
• The sex ratio tends to decrease over the life course (from becoming male-biased to female-biased). This is because women tend to live longer than men.
• It's estimated that today there are over 130 million 'missing women' in the world as a result of selective abortion and excess female deaths.
• The banning of sex determination scanning and gender-selective abortion may have limited the increase in sex ratio at birth in some countries, but did not fully address the problem.
• Development can have opposing impacts on sex ratio: there is evidence that the son preference declines with education, but this often goes hand-in-hand with declining fertility rates and increased access to selective technologies (which can increase the sex ratio).