Sex-selective technology, Population Control, Falling Fertility, & Prejudice imperil the girl child Print E-mail

 UK ~ March 4th 2010


The worldwide war on baby girls

Technology, declining fertility and ancient prejudice are combining to unbalance societies
Scroll down to also read a 2009 BMJ Editorial and Research study on the "Ratio of males to females in China"

XINRAN XUE, a Chinese writer, describes visiting a peasant family in the Yimeng area of Shandong province. The wife was giving birth. “We had scarcely sat down in the kitchen”, she writes, “when we heard a moan of pain from the bedroom next door…The cries from the inner room grew louder­and abruptly stopped. There was a low sob, and then a man’s gruff voice said accusingly: ‘Useless thing!’

“Suddenly, I thought I heard a slight movement in the slops pail behind me,” Miss Xinran remembers. “To my absolute horror, I saw a tiny foot poking out of the pail. The midwife must have dropped that tiny baby alive into the slops pail! I nearly threw myself at it, but the two policemen [who had accompanied me] held my shoulders in a firm grip. ‘Don’t move, you can’t save it, it’s too late.’

“‘But that’s...murder...and you’re the police!’ The little foot was still now. The policemen held on to me for a few more minutes. ‘Doing a baby girl is not a big thing around here,’ [an] older woman said comfortingly. ‘That’s a living child,’ I said in a shaking voice, pointing at the slops pail. ‘It’s not a child,’ she corrected me. ‘It’s a girl baby, and we can’t keep it. Around these parts, you can’t get by without a son. Girl babies don’t count.’”

In January 2010 the Chinese Academy of Social Sciences (CASS) showed what can happen to a country when girl babies don’t count. Within ten years, the academy said, one in five young men would be unable to find a bride because of the dearth of young women­a figure unprecedented in a country at peace.

The number is based on the sexual discrepancy among people aged 19 and below. According to CASS, China in 2020 will have 30m-40m more men of this age than young women. For comparison, there are 23m boys below the age of 20 in Germany, France and Britain combined and around 40m American boys and young men. So within ten years, China faces the prospect of having the equivalent of the whole young male population of America, or almost twice that of Europe’s three largest countries, with little prospect of marriage, untethered to a home of their own and without the stake in society that marriage and children provide.

Gendercide­to borrow the title of a 1985 book by Mary Anne Warren­is often seen as an unintended consequence of China’s one-child policy, or as a product of poverty or ignorance. But that cannot be the whole story. The surplus of bachelors­called in China guanggun, or “bare branches”­ seems to have accelerated between 1990 and 2005, in ways not obviously linked to the one-child policy, which was introduced in 1979. And, as is becoming clear, the war against baby girls is not confined to China.

Parts of India have sex ratios as skewed as anything in its northern neighbour. Other East Asian countries­South Korea, Singapore and Taiwan­have peculiarly high numbers of male births. So, since the collapse of the Soviet Union, have former communist countries in the Caucasus and the western Balkans. Even subsets of America’s population are following suit, though not the population as a whole.

The real cause, argues Nick Eberstadt, a demographer at the American Enterprise Institute, a think-tank in Washington, DC, is not any country’s particular policy but “the fateful collision between overweening son preference, the use of rapidly spreading prenatal sex-determination technology and declining fertility.” These are global trends. And the selective destruction of baby girls is global, too.

Boys are slightly more likely to die in infancy than girls. To compensate, more boys are born than girls so there will be equal numbers of young men and women at puberty. In all societies that record births, between 103 and 106 boys are normally born for every 100 girls. The ratio has been so stable over time that it appears to be the natural order of things.

That order has changed fundamentally in the past 25 years. In China the sex ratio for the generation born between 1985 and 1989 was 108, already just outside the natural range. For the generation born in 2000-04, it was 124 (ie, 124 boys were born in those years for every 100 girls). According to CASS the ratio today is 123 boys per 100 girls. These rates are biologically impossible without human intervention.

The national averages hide astonishing figures at the provincial level. According to an analysis of Chinese household data carried out in late 2005 and reported in the British Medical Journal *, only one region, Tibet, has a sex ratio within the bounds of nature. Fourteen provinces­mostly in the east and south­have sex ratios at birth of 120 and above, and three have unprecedented levels of more than 130. As CASS says, “the gender imbalance has been growing wider year after year.”

The BMJ study also casts light on one of the puzzles about China’s sexual imbalance. How far has it been exaggerated by the presumed practice of not reporting the birth of baby daughters in the hope of getting another shot at bearing a son? Not much, the authors think. If this explanation were correct, you would expect to find sex ratios falling precipitously as girls who had been hidden at birth start entering the official registers on attending school or the doctor. In fact, there is no such fall. The sex ratio of 15-year-olds in 2005 was not far from the sex ratio at birth in 1990. The implication is that sex-selective abortion, not under-registration of girls, accounts for the excess of boys.
Other countries have wildly skewed sex ratios without China’s draconian population controls (see chart 1). Taiwan’s sex ratio also rose from just above normal in 1980 to 110 in the early 1990s; it remains just below that level today. During the same period, South Korea’s sex ratio rose from just above normal to 117 in 1990­then the highest in the world­before falling back to more natural levels. Both these countries were already rich, growing quickly and becoming more highly educated even while the balance between the sexes was swinging sharply towards males.

South Korea is experiencing some surprising consequences. The surplus of bachelors in a rich country has sucked in brides from abroad. In 2008, 11% of marriages were “mixed”, mostly between a Korean man and a foreign woman. This is causing tensions in a hitherto homogenous society, which is often hostile to the children of mixed marriages. The trend is especially marked in rural areas, where the government thinks half the children of farm households will be mixed by 2020. The children are common enough to have produced a new word: “Kosians”, or Korean-Asians.

China is nominally a communist country, but elsewhere it was communism’s collapse that was associated with the growth of sexual disparities. After the Soviet Union imploded in 1991, there was an upsurge in the ratio of boys to girls in Armenia, Azerbaijan and Georgia. Their sex ratios rose from normal levels in 1991 to 115-120 by 2000. A rise also occurred in several Balkan states after the wars of Yugoslav succession. The ratio in Serbia and Macedonia is around 108. There are even signs of distorted sex ratios in America, among various groups of Asian-Americans. In 1975, calculates Mr Eberstadt, the sex ratio for Chinese-, Japanese- and Filipino-Americans was between 100 and 106. In 2002, it was 107 to 109.

But the country with the most remarkable record is that other supergiant, India. India does not produce figures for sex ratios at birth, so its numbers are not strictly comparable with the others. But there is no doubt that the number of boys has been rising relative to girls and that, as in China, there are large regional disparities. The north-western states of Punjab and Haryana have sex ratios as high as the provinces of China’s east and south. Nationally, the ratio for children up to six years of age rose from a biologically unexceptionable 104 in 1981 to a biologically impossible 108 in 2001. In 1991, there was a single district with a sex ratio over 125; by 2001, there were 46.

Conventional wisdom about such disparities is that they are the result of “backward thinking” in old-fashioned societies or­in China­of the one-child policy. By implication, reforming the policy or modernising the society (by, for example, enhancing the status of women) should bring the sex ratio back to normal. But this is not always true and, where it is, the road to normal sex ratios is winding and bumpy.

Not all traditional societies show a marked preference for sons over daughters. But in those that do­especially those in which the family line passes through the son and in which he is supposed to look after his parents in old age­a son is worth more than a daughter. A girl is deemed to have joined her husband’s family on marriage, and is lost to her parents. As a Hindu saying puts it, “Raising a daughter is like watering your neighbours’ garden.”

“Son preference” is discernible­overwhelming, even­in polling evidence. In 1999 the government of India asked women what sex they wanted their next child to be. One third of those without children said a son, two-thirds had no preference and only a residual said a daughter. Polls carried out in Pakistan and Yemen show similar results. Mothers in some developing countries say they want sons, not daughters, by margins of ten to one. In China midwives charge more for delivering a son than a daughter.

Chasing puppy-dogs’ tails

The unusual thing about son preference is that it rises sharply at second and later births (see chart 2). Among Indian women with two children (of either sex), 60% said they wanted a son next time, almost twice the preference for first-borns. This reflected the desire of those with two daughters for a son. The share rose to 75% for those with three children. The difference in parental attitudes between first-borns and subsequent children is large and significant.

Until the 1980s people in poor countries could do little about this preference: before birth, nature took its course. But in that decade, ultrasound scanning and other methods of detecting the sex of a child before birth began to make their appearance. These technologies changed everything. Doctors in India started advertising ultrasound scans with the slogan “Pay 5,000 rupees ($110) today and save 50,000 rupees tomorrow” (the saving was on the cost of a daughter’s dowry). Parents who wanted a son, but balked at killing baby daughters, chose abortion in their millions.

The use of sex-selective abortion was banned in India in 1994 and in China in 1995. It is illegal in most countries (though Sweden legalised the practice in 2009). But since it is almost impossible to prove that an abortion has been carried out for reasons of sex selection, the practice remains widespread. An ultrasound scan costs about $12, which is within the scope of many­perhaps most­Chinese and Indian families. In one hospital in Punjab, in northern India, the only girls born after a round of ultrasound scans had been mistakenly identified as boys, or else had a male twin.

The spread of fetal-imaging technology has not only skewed the sex ratio but also explains what would otherwise be something of a puzzle: sexual disparities tend to rise with income and education, which you would not expect if “backward thinking” was all that mattered. In India, some of the most prosperous states­Maharashtra, Punjab, Gujarat­have the worst sex ratios. In China, the higher a province’s literacy rate, the more skewed its sex ratio. The ratio also rises with income per head.

In Punjab Monica Das Gupta of the World Bank discovered that second and third daughters of well-educated mothers were more than twice as likely to die before their fifth birthday as their brothers, regardless of their birth order. The discrepancy was far lower in poorer households. Ms Das Gupta argues that women do not necessarily use improvements in education and income to help daughters. Richer, well-educated families share their poorer neighbours’ preference for sons and, because they tend to have smaller families, come under greater pressure to produce a son and heir if their first child is an unlooked-for daughter **.

So modernisation and rising incomes make it easier and more desirable to select the sex of your children. And on top of that smaller families combine with greater wealth to reinforce the imperative to produce a son. When families are large, at least one male child will doubtless come along to maintain the family line. But if you have only one or two children, the birth of a daughter may be at a son’s expense. So, with rising incomes and falling fertility, more and more people live in the smaller, richer families that are under the most pressure to produce a son.

In China the one-child policy increases that pressure further. Unexpectedly, though, it is the relaxation of the policy, rather than the policy pure and simple, which explains the unnatural upsurge in the number of boys.

In most Chinese cities couples are usually allowed to have only one child­the policy in its pure form. But in the countryside, where 55% of China’s population lives, there are three variants of the one-child policy. In the coastal provinces some 40% of couples are permitted a second child if their first is a girl. In central and southern provinces everyone is permitted a second child either if the first is a girl or if the parents suffer “hardship”, a criterion determined by local officials. In the far west and Inner Mongolia, the provinces do not really operate a one-child policy at all. Minorities are permitted second­sometimes even third­children, whatever the sex of the first-born (see map).

The provinces in this last group are the only ones with close to normal sex ratios. They are sparsely populated and inhabited by ethnic groups that do not much like abortion and whose family systems do not disparage the value of daughters so much. The provinces with by far the highest ratios of boys to girls are in the second group, the ones with the most exceptions to the one-child policy. As the BMJ study shows, these exceptions matter because of the preference for sons in second or third births.

For an example, take Guangdong, China’s most populous province. Its overall sex ratio is 120, which is very high. But if you take first births alone, the ratio is “only” 108. That is outside the bounds of normality but not by much. If you take just second children, however, which are permitted in the province, the ratio leaps to 146 boys for every 100 girls. And for the relatively few births where parents are permitted a third child, the sex ratio is 167. Even this startling ratio is not the outer limit. In Anhui province, among third children, there are 227 boys for every 100 girls, while in Beijing municipality (which also permits exceptions in rural areas), the sex ratio reaches a hard-to-credit 275. There are almost three baby boys for each baby girl.

Ms Das Gupta found something similar in India. First-born daughters were treated the same as their brothers; younger sisters were more likely to die in infancy. The rule seems to be that parents will joyfully embrace a daughter as their first child. But they will go to extraordinary lengths to ensure subsequent children are sons.

The hazards of bare branches
Throughout human history, young men have been responsible for the vast preponderance of crime and violence­especially single men in countries where status and social acceptance depend on being married and having children, as it does in China and India. A rising population of frustrated single men spells trouble.

The crime rate has almost doubled in China during the past 20 years of rising sex ratios, with stories abounding of bride abduction, the trafficking of women, rape and prostitution. A study into whether these things were connected † concluded that they were, and that higher sex ratios accounted for about one-seventh of the rise in crime. In India, too, there is a correlation between provincial crime rates and sex ratios. In “Bare Branches” ††, Valerie Hudson and Andrea den Boer gave warning that the social problems of biased sex ratios would lead to more authoritarian policing. Governments, they say, “must decrease the threat to society posed by these young men. Increased authoritarianism in an effort to crack down on crime, gangs, smuggling and so forth can be one result.”

Violence is not the only consequence. In parts of India, the cost of dowries is said to have fallen (see article). Where people pay a bride price (ie, the groom’s family gives money to the bride’s), that price has risen. During the 1990s, China saw the appearance of tens of thousands of “extra-birth guerrilla troops”­couples from one-child areas who live in a legal limbo, shifting restlessly from city to city in order to shield their two or three children from the authorities’ baleful eye. And, according to the World Health Organisation, female suicide rates in China are among the highest in the world (as are South Korea’s). Suicide is the commonest form of death among Chinese rural women aged 15-34; young mothers kill themselves by drinking agricultural fertilisers, which are easy to come by. The journalist Xinran Xue thinks they cannot live with the knowledge that they have aborted or killed their baby daughters.

Some of the consequences of the skewed sex ratio have been unexpected. It has probably increased China’s savings rate. This is because parents with a single son save to increase his chances of attracting a wife in China’s ultra-competitive marriage market. Shang-Jin Wei of Columbia University and Xiaobo Zhang of the International Food Policy Research Institute in Washington, DC, compared savings rates for households with sons versus those with daughters. “We find not only that households with sons save more than households with daughters in all regions,” says Mr Wei, “but that households with sons tend to raise their savings rate if they also happen to live in a region with a more skewed sex ratio.” They calculate that about half the increase in China’s savings in the past 25 years can be attributed to the rise in the sex ratio. If true, this would suggest that economic-policy changes to boost consumption will be less effective than the government hopes.

Over the next generation, many of the problems associated with sex selection will get worse. The social consequences will become more evident because the boys born in large numbers over the past decade will reach maturity then. Meanwhile, the practice of sex selection itself may spread because fertility rates are continuing to fall and ultrasound scanners reach throughout the developing world.

Yet the story of the destruction of baby girls does not end in deepest gloom. At least one country­South Korea­has reversed its cultural preference for sons and cut the distorted sex ratio (see chart 3). There are reasons for thinking China and India might follow suit.

South Korea was the first country to report exceptionally high sex ratios and has been the first to cut them. Between 1985 and 2003, the share of South Korean women who told national health surveyors that they felt “they must have a son” fell by almost two-thirds, from 48% to 17%. After a lag of a decade, the sex ratio began to fall in the mid-1990s and is now 110 to 100. Ms Das Gupta argues that though it takes a long time for social norms favouring sons to alter, and though the transition can be delayed by the introduction of ultrasound scans, eventually change will come. Modernisation not only makes it easier for parents to control the sex of their children, it also changes people’s values and undermines those norms which set a higher store on sons. At some point, one trend becomes more important than the other.

It is just possible that China and India may be reaching that point now. The census of 2000 and the CASS study both showed the sex ratio stable at around 120. At the very least, it seems to have stopped rising. Locally, Ms Das Gupta argues †††, the provinces which had the highest sex ratios (and have two-thirds of China’s population) have seen a deceleration in their ratios since 2000, and provinces with a quarter of the population have seen their ratios fall. In India, one study found that the cultural preference for sons has been falling, too, and that the sex ratio, as in much of China, is rising more slowly. In villages in Haryana, grandmothers sit veiled and silent while men are present. But their daughters sit and chat uncovered because, they say, they have seen unveiled women at work or on television so much that at last it seems normal to them.

Ms Das Gupta points out that, though the two giants are much poorer than South Korea, their governments are doing more than it ever did to persuade people to treat girls equally (through anti-discrimination laws and media campaigns). The unintended consequences of sex selection have been vast. They may get worse. But, at long last, she reckons, “there seems to be an incipient turnaround in the phenomenon of ‘missing girls’ in Asia.”
* “China’s excess males, sex selective abortion and one child policy”, by Wei Xing Zhu, Li Lu and Therese Hesketh. BMJ 2009

** “Why is son preference so persistent in East and South Asia?” By Monica Das Gupta, Jiang Zhenghua, Li Bohua, Xie Zhenming, Woojin Chung and Bae Hwa-Ok. World Bank, Policy Research Working Paper 2942.

† “Sex ratios and crime: evidence from China’s one-child policy”, by Lena Edlund, Hongbin Li, Junjian Yi and Junsen Zhang. Institute for the Study of Labour, Bonn. Discussion Paper 3214

†† “Bare Branches”, by Valerie Hudson and Andrea den Boer. MIT Press, 2004

†† † “Is there an incipient turnaround in Asia’s “missing girls” phenomenon?” By Monica Das Gupta, Woojin Chung and Li Shuzhuo. World Bank, Policy Research Working Paper 4846.
 2009; 338: pages 889-890 (18 April 2009)


Ratio of males to females in China

Is still high, but only partly because of the one child policy

China’s one child policy is one of the most controversial social policies ever implemented. The policy reduced the fertility rate and has helped raise living standards for most people in China, but it has been heavily criticised for violating human rights and having many negative social consequences, one of which is an excess number of male births. 1

In the linked study (doi: 10.1136/bmj.b1211), Zhu and colleagues assess trends and geographical patterns in the sex ratio at birth and in people under 20 years of age in China, in addition to the influence of sex selective abortion and the one child policy. 2 They find that in 2005 China had more than 32 million excess males under the age of 20, and over 1.1 million excess male births. The authors present a discouraging picture of very high and worsening male to female ratios in the reproductive age group in China for the next two decades.

By showing that sex ratios for different age groups and places of residence vary with how the one child policy is implemented, the study confirms that the policy is partially responsible for the current imbalance in the sex ratio in China. However, given that the policy is not an independent factor, the extent to which it accounts for the high male to female sex ratio is uncertain.

China, like other East Asian countries, has a cultural tradition of a preference for sons. In these countries, people think that only sons can continue the family line, and sons­rather than daughters­are responsible for their parents in illness and old age. Although it is well documented that this preference for sons is the cause of the high male to female ratio, 3 the preference itself does not directly lead to this high ratio. A preference for sons can affect the sex ratio only in the presence of widespread access to sex selective technology (for example, ultrasound) and a reduced fertility rate (by choice or by coercion). When large family size is the norm and access to contraception is limited, a preference for sons increases the fertility rate but has little effect on the sex ratio. When family sizes are small, irrespective of whether this is voluntary or compulsory, a preference for sons encourages the use of sex selection to ensure the desired number of sons are born. 4

The tradition of a preference for sons was mainly responsible for China’s high birth rate in the past, when large family size was normal and access to contraception and sex selective measures was limited. The one child policy was introduced to bring the high rate of population growth under control through fostering a culture of voluntarily having a small family. However, the policy itself is only partially responsible for the reduction in the total fertility rate. From the 1970s, before the policy was imposed, China saw an emerging culture of having a small family as a result of social and economic developments. The most dramatic decrease in the fertility rate, from 5.9 to 2.9, occurred between 1970 and 1979. 5 After the one child policy was introduced in 1979, the rate fell more gradually, and since 1995 it has stabilised at around 1.7. 6 It has therefore been suggested that China’s total fertility rate would have decreased even without the one child policy. 1 This large reduction in the fertility rate, whether by choice or by coercion, has inevitably increased the male to female ratio because of the preference for sons and the availability of contraception and sex selective measures. These changes in the sex ratio would probably have occurred even without the one child policy, but their effects would probably have been less serious. 7 This idea is supported by neighbouring countries in East Asia, which have no restriction on family size but have the same preference for sons as China; these countries have some of the lowest total fertility rates in the world but also have extremely high ratios of boys to girls at birth. 1

China’s high ratio of males to females would have persisted if attitudes towards female offspring had not changed. 7 Encouragingly, it seems that the tradition of preferring sons is shifting with the socioeconomic changes that come with urbanisation and industrialisation. For example, more and more young women in the cities claim to prefer a small family, and­more importantly­they have no preference for one sex over the other. 8 Indeed, Zhu and colleagues report a decrease in the male to female ratio for the 2005 cohort, 2 which may indicate the beginning of a reduction in the male to female sex ratio for the future.

China can learn much from its neighbouring countries about reversing the worsening sex ratio. Korea was the first country to report very high male to female ratios at birth because of the preference for sons and the widespread use of sex selective technology. In 1992, the male to female ratio for fourth births in South Korea was an astounding 229:100, in sharp contrast to the overall ratio of 114:100. From the mid-1990s, however, a public awareness campaign warning of the dangers of such distortion, combined with strictly enforced laws forbidding sex selection technology, has led to a decline in the male to female ratio from 116:100 in 1998 to 110:100 in 2004. 4

Tao Liu, associate professor, Xing-yi Zhang, professor of thoracic surgery, vice president

1 The Second Teaching Hospital, Jilin University, Changchun 130041, PR China Email:

Competing interests: None declared.

Provenance and peer review: Commissioned; not externally peer reviewed.

Hesketh T, Lu L, Zhu WX. The effect of China’s one-child family policy after 25 years. N Engl J Med 2005;353:1171-6. [Free Full Text]
Zhu WX, Lu L, Hesketh T. China’s excess males, sex selective abortion, and one child policy: analysis of data from 2005 national intercensus survey. BMJ 2009;338:b1211. [Abstract/Free Full Text]
Hesketh T, Zhu WX. Abnormal sex ratios in human populations: causes and consequences. Proc Natl Acad Sci USA 2006;36:13271-5.
Park CB, Cho NH. Consequences of son preference in a low fertility society: imbalance of the sex ratio at birth in Korea. Pop Dev Rev 1995;2:59-84.
Hesketh T, Zhu WX. The one child family policy: the good, the bad, and the ugly. BMJ 1997;314:1685-7. [Abstract/Free Full Text]
Wang JY. Evaluation of the fertility of Chinese women during 1990-2000. In: Theses collection of 2001 national family planning and reproductive health survey. Beijing: China Population Publishing House, 2003:1-15.
Ding QJ, Hesketh T. Family size, fertility preferences, and sex ratio in China in the era of the one child family policy: results from national family planning. BMJ 2006;333:371-3. [Abstract/Free Full Text]
Lin B. Fertility desires of women of childbearing age and influencing factors. In: Theses collection of 2001 national family planning and reproductive health survey. Beijing: China Population Publishing House, 2003:57-65.
 2009; 338:b1211 (9 April 2009)


China’s excess males, sex selective abortion, and one child policy: analysis of data from 2005 national intercensus survey

Wei Xing Zhu, professor1, Li Lu, professor and head of department2, Therese Hesketh, senior lecturer3

1 College of Law, Political Science and Public Administration, Zhejiang Normal University, Jinhua, Zhejiang 310347, China, 2 Institute of Social and Family Medicine, Zhejiang University, Hangzhou 310016, China, 3 Centre for International Health and Development, University College London, London WC1N 1EH

Correspondence to: T Hesketh < >

Objectives To elucidate current trends and geographical patterns in the sex ratio at birth and in the population aged under 20 in China and to determine the roles played by sex selective abortion and the one child policy.

Design Analysis of household based cross sectional population survey done in November 2005.

Setting All of China’s 2861 counties.

Population 1% of the total population, selected to be broadly representative of the total.

Main outcome measure Sex ratio defined as males per 100 females.

4 764 512 people under the age of 20 were included. Overall sex ratios were high across all age groups and residency types, but they were highest in the 1-4 years age group, peaking at 126 (95% confidence interval 125 to 126) in rural areas. Six provinces had sex ratios of over 130 in the 1-4 age group. The sex ratio at birth was close to normal for first order births but rose steeply for second order births, especially in rural areas, where it reached 146 (143 to 149). Nine provinces had ratios of over 160 for second order births. The highest sex ratios were seen in provinces that allow rural inhabitants a second child if the first is a girl. Sex selective abortion accounts for almost all the excess males. One particular variant of the one child policy, which allows a second child if the first is a girl, leads to the highest sex ratios.

Conclusions In 2005 males under the age of 20 exceeded females by more than 32 million in China, and more than 1.1 million excess births of boys occurred. China will see very high and steadily worsening sex ratios in the reproductive age group over the next two decades. Enforcing the existing ban on sex selective abortion could lead to normalisation of the ratios.

In the absence of intervention, the sex ratio at birth is consistent across populations at between 103 and 107 boys born for every 100 girls. 1 2 Higher early mortality among boys ensures a ratio of close to 100 in the all important reproductive years. However, in many countries, mainly in South and East Asia, the sex ratio deviates from this norm because of the tradition of preference for sons. 3 Historically, preference for sons has been manifest postnatally through female infanticide and the neglect and abandonment of girls. 4 Where this persists, it mainly consists of failure to access necessary medical care. 5 6 However, since the early 1980s selection for males prenatally with ultrasonographic sex determination and sex selective abortion has been possible. This technology has become widely available in many countries, leading to high sex ratios from birth. 5 The highest sex ratios are seen in countries with a combination of preference for sons, easy access to sex selective technology, and a low fertility rate, as births of girls must be prevented to allow for the desired number of sons within the family size. 7 In the era of the one child policy the fact that the problem of excess males in China seems to outstrip that of all other countries is perhaps no surprise. 6 8

Some of the evidence for this sex imbalance in China has been challenged, because accurate population based figures have been difficult to obtain. 9 10 Births classified as "illegal," violating the one child policy, may be concealed to avoid penalties. 11 12 Under-reporting of births of girls may be more common in this context, leading to spuriously high sex ratios at birth. 13 14 However, if girls are not reported at birth, they are likely to filter into the statistics later, as registration is necessary for immunisation or to start school. 15 Therefore, examining the sex ratio across different age bands provides a more accurate picture.

The objectives of this study were to elucidate current trends and geographical patterns in the sex ratio at birth and in the population under the age of 20 in China and to explore the role played by sex selective abortion and the one child policy in the sex imbalance.

We analysed data from the intercensus survey of 2005, which was carried out on a representative 1% of the total population in November 2005 and is the most recent national population survey. It used the same basic organisation, procedures, and questionnaire as the fifth census of 2000, but the mode of implementation took into account acknowledged deficiencies of the 2000 census, which led to under-numeration of the population by an estimated 1.8%, mostly in the youngest age groups, resulting in possible inaccuracies in the sex ratio. 16 Specific measures were therefore incorporated into this survey to solve problems of under-numeration, and quality control methods were used to minimise sampling bias. These are described in detail elsewhere. 16 The survey covered all of China’s 2861 counties, using a three stage cluster sampling method at township, village, and enumeration district level, with probability proportionate to estimated size, and is hence broadly representative of the total population. The minimal sampling unit was the enumeration district, which consisted of the village committee in rural areas and the neighbourhood committee in urban areas. The survey was carried out in households by staff specifically trained in census techniques. Only data for the under 20 age group are reported here.

Analysis­The major outcome variable is the sex ratio, defined as males per 100 females. We derived 95% confidence intervals for the sex ratios by using the 95% confidence interval for the proportion of female births (pf) with a variance of pf(1-pf). We calculated the excess of males for all age groups by using an average of the mean sex ratios from 13 countries that have normal secondary sex ratios and little or no sex preference. 17 These were 105 for the 1-9 age group and 104 for the 10-19 age group.

The survey counted 4 764 512 people under the age of 20: 1 073 229 (22%) urban residents, 813 386 (17%) town residents, and 2 877 897 (60%) rural inhabitants. In the 12 months before the study 161 109 births were reported: 23% in urban areas, 17% in towns, and 60% in rural areas. First order births accounted for 63% of the total, second order for 32%, third order for 4.3%, and fourth or higher order for 1%.

Under 20 sex ratio
Table 1 shows the sex ratio by age group and type of residency. Sex ratios were consistently higher than normal across residency type and all age groups except for urban 15-19 year olds. Sex ratios peaked in the 1-4 age group; the highest was 126 (95% confidence interval 125 to 126) in rural areas. Table 2 ?shows the sex ratio by age group for all provinces. Only two provinces, Tibet and Xinjiang, had sex ratios within normal limits across the age range. Two provinces, Jiangxi and Henan, had ratios of over 140 in the 1-4 age group; four provinces­Anhui, Guangdong, Hunan, and Hainan­had ratios of over 130; and seven provinces had ratios between 120 and 129. The provinces with the highest sex ratios are clustered together in the central-southern region (fig 1 ?). Notably, sex ratios were high into the teenage groups in Hainan and Guangxi. The excess of males increased from 5.1% (n=142 634) in the cohort born between 1986 and 1995 to 9.4% (n=184 970) in the cohort born between 1996 and 2005 across the whole country. A marked rise occurred in the percentage of excess males between the two cohorts in all provinces except Xinjiang.

Table 1 Sex ratio (95% confidence interval) by age and residence, under 20 year olds

Table 2 Sex ratios (95% confidence intervals) by age group and province, and excess males

Fig 1 Sex ratio in 1-4 year age group: all China’s provinces

Sex ratio at birth

The total sex ratio at birth for the 12 months to October 2005 was 120 (119 to 121) for the whole sample (table 3 ?), with a gradient between urban (115, 113 to 117), town (120, 118 to 122), and rural (123, 121 to 124) areas. This equates to 11 320 excess boys born for the year for the whole sample. The total sex ratio at birth was over 130 in three provinces (Shaanxi, Anhui, and Jiangxi) and over 120 in 14 provinces. These overall figures conceal dramatic differences in sex ratio at birth by birth order. The sex ratio at birth for first order births was slightly high in cities and towns but was within normal limits in rural areas. However, the ratio rose very steeply for second and higher order births in cities 138 (132 to 144), towns 137 (131 to 143), and rural areas 146 (143 to 149), although the numbers of second order births in cities were low. These rises were consistent across all provinces, except Tibet, with very high figures for second births in Anhui (190, 176 to 205) and Jiangsu (192, 174 to 212). For third births, the sex ratio rose to over 200 in four provinces, although third births accounted for only 4.3% of the total.

Table 3 Sex ratios at birth by birth order for November 2004 to October 2005

The findings paint a discouraging picture of very high and increasing sex ratios in the reproductive age group in China for the next two decades. The sex ratio increased steadily from 108 (108 to 109) in the cohort born between 1985 and 1989 to 124 (123 to 124) in the 2000 to 2004 cohort. However, the ratio then declined to 119 (119 to 120) for the 2005 cohort, perhaps indicating the beginning of a reduction in sex ratios for the future. Sex ratios were outside the normal range for almost all age groups in almost all provinces. The sex ratios rose dramatically between first and second order births, with very high sex ratios for the very few higher order births. Tibet and Xinjiang were the notable exceptions. The highest ratios were seen in the centre and south of the country, in the highly populous provinces of Henan, Jiangxi, Anhui, Guangdong, and Hainan. Extrapolating from this 1% sample to the whole country, we estimate that an excess of 1 132 000 boys were born in the 12 months to October 2005 and that an excess of 32 706 400 males under the age of 20 existed in the whole of China at that time, 18 497 000 of them under the age of 10.

This is the most recent nationwide demographic survey in China, a country undergoing rapid socioeconomic change, where timely data are of particular importance. The survey used specific measures to attempt to ensure coverage of the target group, in order to more accurately estimate the sex ratio. 16 A very large survey aiming to represent 1% of the total population obviously has some limitations. Complete coverage of households and inhabitants is clearly impossible on such a large scale. Furthermore, extrapolation to the whole population from a 1% sample should be done with caution. The small sample size at provincial level in some age bands and for second and higher order births leads to wide confidence intervals, illustrating the uncertainty around these figures. However, the overall credibility of the data is increased by the high sex ratios in older age groups, for which concealment and under-reporting of girls would be difficult, and by the number of births counted for the 12 months to October 2005 (161 109), which matches the estimate of 16 million births a year from other sources. 18 The findings increase our understanding of the roles of sex selective abortion and the influence of the one child policy in the sex imbalance in China and have clear policy implications.

Role of sex selective abortion
The precise role of sex selective abortion in the sex imbalance has been unclear, not least because the practice is illegal in China and obtaining reliable figures is therefore difficult. Some small rural studies have made estimates for proportions of sex selective abortions from hospital based and community birth records. 19 20 21 Two concluded that sex selective abortion was the major cause of the sex imbalance; however, local circumstances vary hugely in China, so wider inferences need to be made with caution. The findings of this survey help to elucidate the role of sex selective abortion in the high sex ratio at the national level.

Firstly, if under-registration of girls, rather than sex selective abortion, accounted for most of the excess births of boys, then sex ratios would fall from birth through early childhood, as girls are required to be registered for immunisation and school entry. 15 Our finding that the sex ratios for the 1-4 year old cohort are higher than those at birth and in infancy tends to refute this hypothesis, suggesting that the rise in the 1-4 age group is a cohort effect­that is, it reflects the higher sex ratio at birth in this cohort. To further investigate the role of under-registration, comparison can be made between each cohort specific sex ratio and the corresponding sex ratio at birth from previous census data. 22 23 This shows that with only one exception, the 15-19 year old cohort born between 1985 and 1989, the sex ratio at birth was higher or very close to the sex ratio of the corresponding birth cohort in the 2005 survey: the age 1-4 cohort had a sex ratio of 124 and a sex ratio at birth of 120, the 5-9 cohort had a sex ratio of 119 and a sex ratio at birth of 118, the corresponding ratios for the 10-14 cohort were 114 and 112, and those for the 15-19 cohort were 108 and 111. This lends support to the assertion that under-registration of girls is not a major contributor to high sex ratios at birth. Infanticide is of course another possible explanation for girls missing at birth, but this is widely acknowledged to be very rare now. 24 25 26 27

Secondly, the dramatic increase in sex ratio with second births that our data document, shows that couples are selecting to ensure a boy, the so called "at least one son practice." 15 In urban areas where few couples are allowed a second child, the high sex ratio for first order births (110, 95% confidence interval 107 to 113) suggests some sex selection occurring with the only child. This pattern of dramatic increases in sex ratios for second children is not unique to China. In both South Korea and parts of India, where overall sex ratios are high, the sex ratio increases dramatically for second and higher order births, which has been attributed to sex selective abortion, as couples try to ensure the birth of male offspring while limiting their family size. 7 28

Thirdly, the steady rise in sex ratios across the birth cohorts since 1986 mirrors the increasing availability of ultrasonography over that period. The first ultrasound machines were used in the early 1980s; they reached county hospitals by the late 1980s and then rural townships by the mid-1990s. 21 29 Since then, ultrasonography has been very cheap and available even to the rural poor. Termination of pregnancy is also very available, in line with the one child policy. 26 Although sex selective abortion is illegal, proving that an abortion has been carried out on sex selective as opposed to family planning grounds is often difficult when abortion itself is so readily available. 21

Role of one child policy
The relation between the sex ratio and the one child policy is a complex one. This study covers births taking place after the policy was instigated, so the increase in sex ratio that we document across age cohorts born in the past 20 years cannot be blamed on the policy in itself. However, the policy is implemented differently across the country (fig 2 ?), and our data do suggest that the sex ratio is related to the way in which the policy is implemented. 15 Whereas in most cities only one child is allowed, three main variants of the policy exist in rural areas. Type 1 provinces are most restrictive­around 40% of couples are allowed a second child but generally only if the first is a girl. In type 2 provinces everyone is allowed a second child if the first is a girl or if parents with one child experience "hardship," the definition of which is open to interpretation by local officials. Type 3 provinces are most permissive, allowing couples a second child and sometimes a third, irrespective of sex. Our data show that the type 2 variant, which allows couples a second child after a girl, results in the highest sex ratios for second order births and the overall highest sex ratios, as seen in Henan, Anhui, Jiangxi, Hunan, Guangdong, and Hainan. These are largely more traditional, predominantly agricultural provinces, where bearing sons is still seen as necessary for long term security. 21 29

Fig 2 Variation in implementation of the one child policy 15

Medium sex ratios were most common in the strict type 1 provinces. However, these provinces are also wealthier, levels of education are higher, especially among women, traditional values of preference for sons are changing, and more people have pensions making them less dependent on sons to provide security in old age. 30 A study in 2001 showed that more than 50% of women of reproductive age in such provinces express no preference for a son. 31 The lowest (most normal) ratios are seen in the type 3, most permissive, provinces, such as Tibet, Xinjiang, and Ningxia. However, these provinces are also sparsely populated and poor, inhabited partly by ethnic groups who are generally less inclined to prefer sons and less accepting of abortion . 29

This analysis is inevitably simplistic, given intra-provincial diversity, but the findings do point to the tendency for the type 2 variant of the policy to result in high sex ratios. The policy implications are clear: changing the regulations in force in type 2 provinces, which permit most couples a second child after a female birth, could help to reduce the sex ratio. Indeed, some commentators have gone further: now that the fertility rate is below replacement, some have recommended that all couples should be allowed two children irrespective of sex, 30 31 32 and relaxation of the policy is expected over the next decade.

Although some imaginative and extreme solutions have been suggested, 33 34 nothing can be done now to prevent this imminent generation of excess men. The government is very aware of the problem and has openly expressed concerns about the consequences of large numbers of excess men for societal stability and security. 22 As early as 2000 the government launched a range of policies to specifically counter the sex imbalance, the "care for girls" campaign. This includes changes in laws in areas such as inheritance by females, as well as an educational campaign to promote gender equality. These measures have had some success, with reports of lower sex ratios at birth in targeted localities. 22 This shows that change is occurring. In addition, the finding that the sex ratio at birth did not increase between 2000 and 2005, and that the ratio for the first (and usually only) birth in many urban areas is within normal limits, means that the sex ratio may fall in the foreseeable future.

What is already known on this topic
  • The reported sex ratio (males per 100 females) in China is high, but accurate population based figures for actual sex ratios have been notoriously difficult to obtain
  • The role of sex selective abortion and the influence of the one child policy on the sex imbalance have been unclear

What this study adds
  • China will see very high and steadily worsening sex ratios in the reproductive age group for the next two decades
  • Sex selective abortion accounts for almost all the excess males
  • One particular variant of the one child policy leads to the highest sex ratios

Contributors: All the authors participated in the analysis and in preparing the tables and saw and approved the final version of the paper. ZWX is the guarantor.

Funding: This study was funded through a China-UK excellence fellowship for TH from the Department of Innovation, Universities and Skills.

Competing interests: None declared.

Ethical approval: Not needed.

James WH. The human sex ratio. Part 1: a review of the literature. Human Biology 1987;59:721-5. [Web of Science] [Medline]
Teitelbaum M. Factors affecting the sex ratio in large populations. J Bio Sci 1970:2:61-71.
Arnold F. The effect of son preference on fertility and family planning: empirical evidence. Popul Bull UN 1987;23:44-55.
Klasen S, Wink C. A turning point in gender bias in mortality? An update on the number of missing women. Popul Dev Rev 2002;28:285-312. [CrossRef] [Web of Science]
Sen A. Missing women revisited. BMJ 2003;327:1297-8. [Free Full Text]
Hesketh T, Zhu WX. Abnormal sex ratios in human populations: causes and consequences. Proc Natl Acad Sci USA 2006;103:13271-5. [Abstract/Free Full Text]
Park CB, Cho NH. Consequences of son preference in a low fertility society: imbalance of the sex ratio at birth in Korea. Popul Dev Rev 1995;21:59-84. [CrossRef] [Web of Science]
Gu B, Roy K. Sex ratio at birth in China, with reference to other areas in East Asia: what we know. Asia Pac Popul J 1995;10:17-42. [Medline]
Short SE, Zhai FY. Looking locally at China’s one-child policy. Stud Fam Plan 1998;29,4:373-87.
Merli MG, Raftery AE. Are births underreported in rural china? Manipulation of statistical records in response to China’s population policies. Demography 2000;37:109-26. [Web of Science] [Medline]
Banister J. Shortage of girls in China today. J Popul Res 2004;21:19-45. [CrossRef]
Johansson S, Nygren O. The missing girls of China: a new demographic account. Popul Dev Rev 1991;17:35-51. [CrossRef] [Web of Science]
Zeng Y, Tu P, Gu B, Xu L, Li B, Li Y. Causes and implications of the recent increase in the reported sex ratio at birth in China. Popul Dev Rev 1993;19:283-302. [CrossRef] [Web of Science]
Coale A. Excess female mortality and the balance of the sexes in the population: an estimate of the number of missing females. Popul Dev Rev 1991;17:518.
Attane I. China’s family planning policy: an overview of its past and future. Stud Fam Plan 2002;33:103-13. [CrossRef]
Zhang W, Li X, Cui H. China’s intercensus survey in 2005. Beijing: China Population Publishing House, 2007.
Ulizzi L, Astolfi P, Zonta LA. Sex ratio at reproductive age: changes over the last century in the Italian population. Hum Biol 2001;73:121-8. [CrossRef] [Web of Science] [Medline]
China-Profile. Facts, figures, and analyses. .
Wu Z, Viisainen K, Hemminki E. Determinants of high sex ratio among newborns: a cohort study from rural Anhui Province. Reprod Health Matters 2006;14:172-80. [CrossRef] [Web of Science] [Medline]
Lofstedt P, Luo SS, Johansson A. Abortion patterns and reported sex ratio in rural Yunnan, China. Reprod Health Matters 2004;12:86-95. [CrossRef] [Web of Science] [Medline]
Chu JH. Prenatal sex determination and sex-selective abortion in rural central China. Popul Dev Rev 2001;27:259-81. [CrossRef] [Web of Science]
Li S. Imbalanced sex ratio at birth and comprehensive intervention in China. Presentation at 4th Asia Pacific Conference on Reproductive and Sexual Health and Rights, Hyderabad, 29-31 October 2007. Available at
China Population Information and Research Centre. Basic population data of China: 1949-2000.
Hesketh T, Zhu WX. The one child family policy: the good, the bad and the ugly. BMJ 1997;314:1685-7. [Abstract/Free Full Text]
Wu ZC, Viisainen K, Wang Y, Hemminki E. Perinatal mortality in rural China: retrospective cohort study. BMJ 2003;327:1319-22. [Abstract/Free Full Text]
Hemminki E, Wu ZC, Cao GY. Illegal births and legal abortions­the case of China. Reprod Health Matters 2005;2:5.
Li S, Zhu C, Feldman M. Gender differences in child survival in contemporary rural China: a county study. J Biosoc Sci 2004;36:83-109. [CrossRef] [Web of Science] [Medline]
Jha P, Kumar R, Vasa P, Dhingra N. Thirichelvam D, Moineddan R. Low male to female sex ratio of children born in India: national survey of 1.1 million households. Lancet 2006:367:211-8.
Li R. An analysis of the sex ratio at birth in impoverished areas in China. Chin J Popul Sci 1998;10:65-73. [Medline]
Winkler EA. Chinese reproductive policy at the turn of the millennium: dynamic stability. Popul Dev Rev 2002;28:379-418. [CrossRef] [Web of Science]
Qu JD, Hesketh T. Family size, sex ratio and fertility preferences in the era of the one child family policy: results from the national family planning and reproductive health survey. BMJ 2006;333:371-3. [Abstract/Free Full Text]
Zeng Y. Options for fertility policy transition in China. Popul Dev Rev 2007;33:215-46. [CrossRef] [Web of Science]
Tuljapurkar S, Li N, Feldman MW. High sex ratios in China’s future. Science 1995;267:874-6. [Abstract/Free Full Text]
Hudson V, Den Boer AM. A surplus of men, a deficit of peace: security and sex ratios in Asia’s largest states. Int Secur 2002;4:5-38.
(Accepted 27 November 2008)

© Zhu et al 2009
This is an open-access article distributed under the terms of the Creative Commons Attribution Non-commercial License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.