China's one-child policy created a generation that prefers smaller families

China’s controversial one-child policy may have officially ended over a decade ago, but its legacy continues to shape Chinese society, according to groundbreaking research that reveals how growing up without siblings has fundamentally altered attitudes towards family size.

Two studies by demographers Dr Shuang Chen, Department of Social Policy at LSE, and Professor Stuart Gietel-Basten, Hong Kong University of Science and Technology, provide the first rigorous evidence that China’s one-child policy has created an intergenerational “low-fertility trap”. Today’s only children, having experienced life in small families, now prefer to have fewer children themselves

Why is China an outlier among low-fertility countries?

These findings arrive at a critical juncture for China, which, in 2022, recorded a population decline for the first time in six decades. The following year, India surpassed it as the world’s most populous nation. Despite Beijing’s increasing attempts to encourage larger families – including financial incentives, extended maternity leave and a shift to a three-child policy in 2021 – the fertility rate continues to plummet. It is currently estimated to be 1.00 births per woman. Replacement level fertility - the number of babies that must be born to sustain the current number of people in the population - is about 2.1 births per woman.

“I’m trying to understand why fertility ideals are so low in urban China, particularly whether the ‘one-child policy’ might have played a role.”

Only children in urban China … grew up without siblings but with exceptionally high levels of parental investment in their education and health.

The appeal of a smaller family

Using sophisticated statistical techniques to analyse data from tens of thousands of Chinese citizens, the researchers drew on two natural experiments: the introduction of the one-child policy in 1980 and its relaxation in 2015. Their approach made it possible to see how policy changes directly affected fertility preferences while controlling for other social and economic factors.

The first paper, published in Population Studies, examines what happened when China ended its one-child policy in October 2015, allowing all couples to have two children. By comparing couples who were newly eligible to have a second child with those who had already been permitted under previous exemptions, the researchers found that relaxing restrictions increased the average stated ideal family size by approximately 0.2 children.

Whilst statistically significant, this modest increase suggests that stated preferences for small families in urban China are largely genuine, rather than merely reflecting political correctness or fear of punishment for expressing higher family size ideals.

If there’s a fundamental change in people’s fertility preferences and aspirations, it’s no longer about financial barriers.

The benefits of being part of a small family

The second study, in the European Journal of Population, delves deeper into the mechanism behind these low fertility preferences. Comparing people born just before and after 1980 when the one-child policy was introduced, the researchers discovered that being an only child reduces one’s ideal family size by 0.6 to 0.7 children, a substantial effect that provides rare empirical support for the “low-fertility trap” hypothesis.

This theory suggests that prolonged periods of low fertility can become self-reinforcing. As family sizes shrink, children grow up with fewer siblings, which shapes their own preferences for smaller families when they reach adulthood. The cycle then repeats, potentially making recovery to higher fertility rates increasingly difficult.

“While we didn’t directly test socialisation mechanisms, we know that family interactions and relationships during childhood have a huge influence on how we form our own families as adults,” Dr Chen said. “The number of siblings – or whether we have any siblings at all – is a crucial part of that early experience. Through observing and interacting with parents and siblings, we develop ideas about what parenthood entails, how to raise children, and the consequences of having a child.

“For only children in urban China specifically, they grew up without siblings but with exceptionally high levels of parental investment in their education and health, and equally high parental expectations for their success. This distinctive childhood experience and relationship help explain why growing up as an only child might lead to a preference for having just one child themselves.”

Rather than attempting to reverse fertility decline, the more realistic and perhaps more urgent task is for societies to adapt to sustained low fertility.

Identifying a low-fertility trap

In most post-industrial societies experiencing below-replacement fertility – from France to Australia – people still report ideal family sizes of two children or more, even if actual fertility is lower. China stands virtually alone in the world in having average ideal family sizes below two, particularly in urban areas.

“The key issue is the gap – or lack thereof – between ideal and actual fertility,” Dr Chen explains. “This gap matters because it indicates how much room there is for policy intervention: if people want more children than they are currently having, policies such as providing financial incentives can help remove some of the barriers. But in urban China, both ideal and actual fertility are low. If there’s a fundamental change in people’s fertility preferences and aspirations, it’s no longer about financial barriers.”

The Chinese government appears undeterred. In August 2022, 17 government agencies jointly issued guidelines promoting a “family-friendly society”, encompassing measures from preferential housing for larger families to restrictions on non-medical abortions. Provincial governments have introduced cash bonuses for second and third children. Yet birth rates continue to fall.

Can China reverse this fertility trend?

Dr Chen is clear about her expectations: “Given the low fertility ideals, I don’t expect any dramatic reversal of the fertility decline in China.”

The implications extend beyond China. Dr Chen explains: “The research also helps us address something that concerns policymakers both within and beyond China, which is whether there exists a ‘low-fertility trap’, whereby low fertility in one generation leads to low fertility ideals and further fertility declines in the subsequent generation.”

Perhaps most provocatively, the research questions whether governments should be trying to raise fertility at all. Dr Chen comments: “There is an important distinction between helping people achieve their fertility desires versus treating low fertility as a problem in and of itself. Many policies, including those the Chinese government has recently introduced, are premised on the first goal: helping people achieve their fertility desires by addressing the gap between the number of children people want and the number they have.

“But if fertility preferences have fundamentally shifted in urban China, increasing fertility is exceptionally difficult. Of course, rapid fertility decline and population aging have important consequences and bring significant challenges. But rather than attempting to reverse fertility decline, the more realistic and perhaps more urgent task is for societies to adapt to sustained low fertility. Policies that support families and enable people to realise their aspirations will continue to play an important role in this process.”

As China confronts its demographic future, these studies provide a sobering reminder that population control policies can have consequences that last generations. The one-child policy, in place for 35 years, may continue to shape Chinese society long after the policy itself has been consigned to history.

Dr Shuang Chen was speaking to Joanna Bale, Senior Media Relations Manager at LSE.

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