Last October, China ended its 35-year-old policy of restricting most urban families to one child. Commonly referred to as the "one-child" policy, the restrictions were actually a collection of rules that governed how many children married couples could have.

"The basic idea was to encourage everybody, by coercion if necessary, to keep to ... one child," journalist Mei Fong tells Fresh Air's Terry Gross.

Fong explores the wide-ranging impact of what she calls the world's "most radical experiment" in her new book, One Child. She says that among the policy's unintended consequences is an acute gender imbalance.

"When you create a system where you would shrink the size of a family and people would have to choose, then people would ... choose sons," Fong says. "Now China has 30 million more men than women, 30 million bachelors who cannot find brides. ... They call them guang guan, 'broken branches,' that's the name in Chinese. They are the biological dead ends of their family."

Fong says the policy also led to forced abortions and the confiscation of children by the authorities. Looking ahead, China is also facing a shortage of workers who can support its aging population.

"Right now China has a dependency ratio of about five working adults to support one retiree. That's pretty good, that's a very healthy ratio. In about 20 years that's going to jump to about 1.6 working adults to support one retiree," Fong says. "The one-child policy drastically reshaped the composition of China's people. So now they have a population that's basically too old and too male and, down the line, maybe too few."

On the economic and cultural implications of losing your only child in China

It means a lot, economically speaking, because a lot of families still don't have any kind of a financial security, so losing one child is basically a pension plan, so that's one thing. For the Chinese, culturally speaking, the continuance of the family line was very important, so when you die without any issue you are basically violating all sorts of duties to your ancestors, which is very important. ... Chinese society is still very family-centric even if it's just a small family size, you're not considered fully an adult until you are married, and you're not considered complete until you have a child, and when you lose that child, you fall quite far down the societal totem pole.

So, for example, this family that I covered that had lost their only child [in an earthquake], they lost a lot of status in their village. They said that their neighbors were avoiding them and shunning them, basically, that they were worried that this childless couple would now be hangers-on, clinging onto them, borrowing money, not having any sort of protection — so that's what losing your one child means.

Today in Chinese context there's a name for these people who have lost their only child, it's called shidu, and it means, "parents who've lost their only child." And for parents who are shidu, some of them find it hard to get admitted into nursing homes. Some nursing homes won't take them. They say, "You have no progeny to authorize treatments or payments or anything, so we'd prefer not to admit you." They also have difficulty buying funeral plots for the same reason. Who is going to service the maintenance costs of your cemetery down the line? So these are very sad issues.

On exceptions to the one-child policy

They would have some certain exceptions, because they found that they could not make everybody keep to that one-child rule without allowing for certain exceptions. So you could technically have a second child if you had a certain job that was hazardous, like if you were a coal miner or a fisherman. You could also have a second child maybe if you were one of China's minority tribes or if you lived in a rural area and your first child was a girl and they recognize that a lot of people want to try for sons. But the end result was that with all of these exceptions coming down the line, a lot of people didn't really necessarily know what the rules were, so it was very easy to contravene them and be fined for them.

On how the one-child policy was enforced

If [a woman] lived in a small village, for example, she would probably be scrutinized by a group, she would probably be grouped together with a set of households and come under what they call a cluster leader, somebody who sort of monitors the progress and fertility rights of a certain set of households. ... So if this woman ... fell pregnant then most likely this cluster leader would know about it very quickly and then she would report to higher up. ... Probably at first a village leader would show up at their doorstep and say, "You know very well you should not have this; you could have all sorts of problem with this. You may have to pay a fine." I've met enforcers who have gone to these houses and say, "We used to take away something valuable to show that we mean business." ... Like a television set, for example, or a pig, or sometimes if the household was a very poor household they'll take away homespun cloth or grain or something, something that had to make it hurt, basically — that was in a village setting, of course.

In a city setting they could maybe, if you worked for a [civil service-like] job they might threaten to fire you. ... This is for having a child. If you went for a termination, all of this would go away. But, of course, then there were people who really wanted the child and then they would try and evade the whole process of being taken away for a forced abortion, because here's the thing: Between your conception and your delivery date, all bets are off — they can make you.

On the aging population in China

The one-child policy drastically reshaped the composition of China's people. So now they have a population that's basically too old and too male and down the line, maybe too few. So the too old issue is that right now China has a dependency ratio of about five working adults to support one retiree. That's pretty good, that's a very healthy ratio. In about 20 years that's going to jump to about 1.6 working adults to support one retiree, and that's because that big population boom that we talked about, that big cohort of people are all living longer and getting older and therefore hitting their 70s, 80s and 90s, so by the time 2050 comes around one in four Chinese people will be a retiree.

The entire population of retirees in China would be the third largest nation in this world, if they were to form their own country. So that has nothing to do with the one-child policy, that's just a function of people living longer and growing older, but the problem is then you have this very small working cohort to support that, and that has everything to do with the one-child policy. You just drastically shrank the number of working adults who support this huge, aging tsunami and that's the problem going ahead.

On technology allowing parents to know the sex of the fetus

In the beginning when the policy came around in 1980, at that time they did not have scanning machines that could determine the gender of the fetus at an early stage, so people who delivered girls, for example, and wanted to keep their quota for that one boy — because if you used up your quota for a girl and then you gave birth to another girl and you would lose that — so people would either abandon their daughters or there would be infanticide, or they would give them away, which is part of the reason why we saw so many adoptions of Chinese babies, mostly girls, in the West.

But later in the 1990s, technology made it easier for people to do all these scans and companies like General Electric made these scanning machines that were portable and small enough that you could go from village to village and you could determine the sex of your fetus ... for as little as $10 or $20, so people would just have an abortion instead of carrying a child to full term. ... The Nobel economist Amartya Sen estimated there were about 100 million missing women, women that were never born or killed or aborted across Asia.

On a generation of women being more educated and professionally successful because of the one-child policy

Let's say you were born after 1980 in a big city, chances are you probably don't have a sibling. And if you're a girl and you don't have a sibling, you don't have to fight with your sibling for resources. So your parents will want to send you to college. They won't be debating a question of whether they should spend the money on your brother or yourself; it's all for you. So imagine this scenario replicated a million times over and the end result is urban women born after 1980 achieved way more than any other generation before them.

Copyright NPR 2018.