AUDIE CORNISH, HOST:

For years, we've heard about a great sex imbalance in China due to the country's one-child policy - way more boys born than girls. It was believed that female fetuses were being aborted, that female infanticide was taking place and that some births were never reported. Now a pair of researchers have written that they believe unreported births account for more of the so-called missing girls than previously thought. John James Kennedy at the University of Kansas says he and his Chinese research partner first heard about this while living in a village in China. They noticed many families had two or more children.

JOHN JAMES KENNEDY: By the mid-1990s, rural families were allowed to have a second child if the first was a girl. So when we are in a - one home, they had three kids. It was an older daughter, the younger son and a middle daughter. They introduced the son and the older daughter by their names, and they introduced the middle daughter as the non-existent one - (speaking Mandarin) - with a nod and a wink. And so then we went - asked them to explain. And they explained that the first daughter was born, registered as a first child. The second daughter was born, and they waited. They had - and did not register that child. Then the third child was born, and they registered that third child as a second child.

CORNISH: Much of the conversation about this, prior to this point, has been that the problem with selective abortion and infanticide. Are you saying that those things didn't happen as much as was previously believed?

KENNEDY: What we suggest is that that did of course happen. And that remains an important explanation and factor. We suggest that the unregistered births tend to make up a larger portion than previously thought.

CORNISH: If there are a bunch of girls out there, what's life like for them not registered?

KENNEDY: We interviewed a number of women who were over 18, who went through most of their teens, even up to their early 20s, without a registration card. They reminisced about when they were young. They were in elementary school, but they called them black kids, meaning if you were a black household - means that you are an unregistered household or you're an unregistered child. So she remembers vividly as being called the one who's not really here. And other kids knew and would make fun of her. But the thing is when they got older, which is more difficult, is being able to get an official job, getting train tickets, being able to get basic social services were much more difficult. They tend to fall through the social cracks.

CORNISH: The one-child policy ended this year. How do you think the environment in China for talking about this is different?

KENNEDY: The fertility rate, actually having less kids, has been going down dramatically over the last three decades - or four decades. And so having fewer kids seems to be the norm over time. We've noticed a cultural change for son preference. So in the past, there was this need for a son to take care of you in your old age. But we've seen a cultural change and the values of daughters have changed and have increased, where daughters can take care of their natal family and their parents. Son preference is not completely gone. However, we see that the traditional values of daughters and traditional view has changed.

CORNISH: John James Kennedy, thank you so much for speaking with us.

KENNEDY: You're welcome.

CORNISH: John James Kennedy is associate professor of political science at the University of Kansas. His research appears in The China Quarterly. Transcript provided by NPR, Copyright NPR.