Just backing up a post by Marcus Roberts the other day, the Canadian Medical Association Journal has just published an article which claims that it will be decades before the natural sex-ratio is restored in parts of India, China and South Korea because of sex-selective abortion and a tradition of son preference:

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 the 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.