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.

Source 1. 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

In short: the one‑child policy interacted with a strong cultural preference for sons and the spread of prenatal sex‑detection technology to create powerful incentives to ensure a family’s single child was male. That produced widespread sex‑selective abortion, underreporting or hiding of female births, and other practices that pushed China’s sex ratio at birth far above normal.

How that happened (mechanisms)
- Son preference + single allowed birth: parents who traditionally wanted at least one son suddenly had only one chance (or one legal, registered chance) to have a male heir. That concentrated pressure on that single birth.
- Widespread access to ultrasound from the mid‑1980s: once fetal sex could be known before birth, some parents aborted female fetuses to try to guarantee a son.
- Underreporting/hiding and informal practices: because of fines, penalties, and social pressure, some families avoided registering daughters, abandoned or neglected female infants, or otherwise hid second births. These practices meant official data undercounted female births for some years.
- Enforcement and local variation: strict enforcement in some places intensified incentives for sex selection; in some rural areas, local exceptions (e.g., allowing a second birth if the first was a girl) produced uneven outcomes and sometimes encouraged clandestine behavior.
- Technology + markets: the sex imbalance also fed illegal markets (trafficking, buying brides) and adoption/abandonment of girls.

Consequences (short and long term)
- Skewed sex ratio at birth: China’s SRB rose well above the biological norm (~105 boys per 100 girls), peaking in the late 1990s–2000s (approaching ~120 in some years). Golley notes this will leave an estimated tens of millions of men “looking for a wife” by 2030.
- “Marriage squeeze”: many men (disproportionately poorer, rural) will have difficulty finding partners, with social and psychological effects and risks of increased crime, trafficking, and instability.
- Social harms and human costs: abandonment, trafficking in women, reduced status and protection for girls in some households, and emotional harm to parents and single children (the 4-2-1 family burden).
- Long-term demographic effects: a distorted sex ratio contributes to population aging and social imbalance that policy changes take years or decades to correct.

So the one‑child policy did not create son preference, but by limiting births it concentrated existing cultural preferences and, together with accessible ultrasound, led to widespread sex selection and a large male surplus that China is still dealing with.