In the next 20 years in large parts of China and India, there will be a 10% to 20% excess of young men because of sex selection and this imbalance will have societal repercussions, states an analysis in CMAJ (Canadian Medical Association Journal).
A preference for sons in China, India and South Korea combined with easy access to sex-selective abortions has led to a significant imbalance between the number of males and females born in these countries. The sex ratio at birth (SRB) the number of boys born to every 100 girls is consistent in human populations in which about 105 males are born to every 100 females. However, with the advent of ultrasounds that enable sex-selection, the sex ratio at birth in some cities in South Korea climbed to 125 by 1992 and is over 130 in several Chinese provinces from Henan in the north to Hainan in the south.
In 2005 in China, "it was estimated that 1.1 million excess males were born across the country and that the number of males under the age of 20 years exceeded the number of females by around 32 million," writes Professor Therese Hesketh, UCL Centre for International Health and Development, London, United Kingdom with coauthors.
In India, similar disparities exist, with sex ratios as high as 125 in Punjab, Delhi and Gujarat in the north but normal sex ratios of 105 in the southern and eastern states of Kerala and Andhra Pradesh.
"A consistent pattern in all three countries is the marked trend related to birth order and the influence of the sex of the preceding child," state the authors. If the first or second born are girls, couples will often sex select to ensure the second or third child is a boy.
The societal implications mean that a significant percentage of the male population will not be able to marry or have children because of a scarcity of women. In China, 94% of unmarried people aged 28 to 49 are male, 97% of whom have not completed high school, and there are worries the inability to marry will result in psychological issues and possibly increased violence and crime.
Policy makers in China, India and South Korea have taken some steps to address the issue, such as instituting laws forbidding fetal sex determination and selective abortion, but more can be done.
"To successfully address the underlying issue of son preference is hugely challenging and requires a multifaceted approach," state the authors.
The relaxation of China's one-child policy, especially in rural areas, could have some impact on sex ratios. But more important is to change underlying and long-standing attitudes towards son preference. Public awareness campaigns have had an impact. In South Korea and China, awareness campaigns have helped reduce the sex ratio at birth (for example, 118 in 1990 in South Korea to 109 in 2004).
"However, these incipient declines will not filter through to the reproductive age group for another two decades, and the SRBs in these countries remain high. It is likely to be several decades before the SRB in countries like India and China are within normal limits," conclude the authors.
Explore further: California's tobacco control efforts losing steam, report finds