The People’s Republic of China has launched it s decennial census, sending 6.5 million representatives to 400 million households across the country. In 2000, China tallied up 1.29 billion people, and demographers estimate the current population at more than 1.33 billion. The one-child policy has been in place for 30 years. Why hasn’t the population declined?

Momentum and lax enforcement. The architects behind China’s one-child policy never expected to cut the population immediately, because the millions of young children born before implementation are now in their reproductive years and having kids faster than the smaller elderly population is dying off. This phenomenon, known as population momentum, creates a 50-60 year gap between a drop in the fertility rate and an actual population decline. In addition, the one-child policy isn’t really a uniform, nationwide prohibition on multiple children. Within three years of the program’s initiation, massive protests in rural areas forced officials to revise the policy, and today the number of children allowed for each parent depends on a variety of factors (more on that below). Lots of couples have two or even three children by exploiting legal loopholes, paying fines, or simply lying to the government.

Chinese family size is dictated by the parents’ backgrounds, location, wealth, and willingness to defraud the government. The one-child policy doesn’t apply to most ethnic minorities, such as the Uighurs, Tibetans, and Kazakhs. (Some members of these groups claim they are forced to comply, despite government assurances to the contrary.) In some provinces, if either one or both parents have no siblings, it’s possible to have two kids. Rural areas typically permit a second child, especially if the first is a girl. Urbanites are the most likely to get caught up in the one-child policy, though even some cities are experimenting with allowing two children. If they really want a big family, wealthy Beijing denizens simply pay a fine to register their second or third child. (The one-time penalty can be up to six times the family’s annual income.) Less affluent parents hide their extra kids, either by sending them away to school or passing them off as nieces and nephews.

China’s population was 981,235,000 in 1980, the year that Deng Xiaopeng launched his family planning campaign. The country has added an average of 12 million people per year since then, the equivalent of birthing the entire population of Greece or Belgium annually. Still, the one-child policy seems to have slowed expansion. China’s annual growth rate of 1.06 percent is one-third less than that of the world’s population over the same period. While a few have argued that the fertility rate would have slowed on its own, the Chinese government claims the policy has prevented 400 million births, more than the population of the United States and Canada combined. Those missing Chinese people would today represent more than five percent of the world’s population—and that’s not counting the children they would have had.

The one-child policy has had demographic impacts beyond population-size control. China now has 32 million more boys than girls under age 20, due to the illegal but widespread practice of sex-selective abortion. Few parents abort a girl the first time around, since they will be allowed another chance at a boy. But among second-born children in rural areas, there are 160 boys born for every 100 girls. The imbalance has accelerated steadily since ultrasound became widely available in the mid-1980s. In the near future, the scarcity of women may have a more profound impact on population growth than any government fine.

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Explainer thanks Susan Greenhalgh of the University of California-Irvine.

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