Question

How did the One-Child policy negatively cause gender imbalance?


Source: Jane Golley, “The Costs and Benefits of China’s One-Child Policy,” The Conversation, November 21, 2013.

The one-child policy has unquestionably caused fertility to decline more rapidly than it otherwise would have...and has therefore played a significant role in China’s demographic transition...explaining up to one- quarter of its per capita GDP growth in the last three decades....
With that rapid GDP growth has come better nutrition, rising levels of education, longer life expectancies, and higher living standards for the vast majority of Chinese people....
This is not to deny the substantial, and in many cases immeasurable, costs of the policy.... Aside from the obvious economic costs of having more dependents and fewer workers in the population, the policy places a huge burden on single Chinese children at the bottom of the resulting “4 - 2 - 1” family structure (four grandparents, two parents and one child).
Even more consequential is the dramatic rise in China’s sex ratio at birth, the costs of which will be borne by an estimated 30 million or more Chinese men who will be looking for a wife in 2030 but unable to find one. The one-child policy–in combination with a traditional preference for sons and widespread access to ultrasound technology to detect gender* since the mid-1980s–is at least partly to blame.
Other significant emotional costs result from not being allowed to determine your family’s size, being coerced into terminating second pregnancies, or giving birth to a second child who is not allowed to enroll in school or to access the healthcare system.
* Ultrasound technology enables doctors and parents to see a picture of the fetus when it is in the mother’s womb. Some Chinese parents chose to abort fetuses that ultrasound revealed to be female.

Answer 1

Short answer: by sharply reducing how many children families were allowed to have, the one‑child policy magnified an existing cultural preference for sons and—once prenatal sex‑selection technology became widely available—led many families to ensure their one permitted child was male. That produced a sustained excess of boys at birth and a large “surplus” of men decades later.

How that happened, in more detail

- Son preference as the starting point
- In much of China, sons have traditionally been preferred because they carry the family name, provide old‑age support, and perform ancestral rites. When families could have many children, the chance of eventually having a son was acceptable; when limited to one child, the pressure to make that child a son rose sharply.

- Access to prenatal sex‑determination and sex‑selective abortion
- Ultrasound and other technologies became widespread from the mid‑1980s. Combined with the one‑child constraint and son preference, many parents chose to terminate pregnancies when the fetus was female. This directly raised the sex ratio at birth (more boys per 100 girls).

- Postnatal mechanisms that worsened imbalance
- Female infanticide, deliberate neglect, and poorer healthcare/nutrition for girls (in some areas) increased female child mortality.
- Some parents hid births of daughters (under‑reporting) to try for another child or avoid fines; that distorted official counts and increased pressure for sex selection when births were finally registered.
- Abandonment and trafficking of girls also occurred in some places.

- Measured effect and scale
- The natural sex ratio at birth is about 103–107 boys per 100 girls. In China, the sex ratio at birth rose well above that level from the 1980s onward and peaked in the 1990s–2000s (commonly reported peaks above 115–120 boys per 100 girls in some years and provinces).
- That excess at birth accumulates into tens of millions more men than women of marriageable age, producing the “marriage squeeze” people like Jane Golley estimate (roughly 30 million or more men who may be unable to find wives by 2030).

Major social and economic consequences
- Large cohorts of unmarried men (“bare branches”) with social and mental‑health impacts and potential effects on stability in some locales.
- Rising demand for brides, higher bride prices, and cross‑border bride trafficking and illegal marriage markets.
- Long‑term demographic problems: fewer women in the population affects birth rates and family formation; combined with population aging, it worsens dependency ratios.
- Gendered social harms: devaluing of girls, worse outcomes for some women and girls.

Caveat: the one‑child policy was a major accelerator, not the sole cause
- Son preference predated the policy, and economic development, urbanization, and local enforcement intensity mattered. But the policy created strong incentives to use sex selection and other measures to ensure a male heir, which markedly worsened the sex ratio.

Policy responses
- China relaxed the policy (to two children, then three) in part to address demographic problems. Effective mitigation also requires enforcing bans on prenatal sex‑selection, changing norms that devalue girls, strengthening social security so parents feel less need for a son as old‑age support, and protecting girls’ rights and health.

If you want, I can show specific year‑by‑year sex‑ratio data, maps of provincial variation, or studies linking the skew to particular social outcomes.