Story highlights A new study finds discrepancies in population data in China

Researchers say millions of "missing girls" were registered later in life

(CNN) It sounds like the plot of a mystery novel.

A controversial one-child policy that resulted in as many as 60 million "missing girls" in China, the most populous country on Earth.

But in a new study, researchers suggest that around 25 million of these girls aren't actually missing, but went unreported at birth -- only appearing on government censuses at a later stage in their lives.

"Most people are using a demographic explanation to say that abortion or infanticide are the reasons (these girls) don't show up in the census and that they don't exist," said John Kennedy, study co-author and political science professor at Kansas University.

"But we find there is a political explanation."

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