A summer view of the Mumbai skyline by the Arabian Sea coast. (Rafiq Maqbool/AP)

What's the most populous nation in the world? For years, the answer to that question was simple and rarely disputed: China. But this week an academic has sparked widespread discussion around the world by making a bold claim — that China's official population estimates were wrong and in fact India was now the world's largest country.

This potentially radical suggestion was made Monday by Yi Fuxian, a researcher at the University of Wisconsin-Madison, during an event at China's Peking University.

According to the South China Morning Post, Yi suggested that China had only 377.6 million new births from 1991 to 2016, far less than the official figure of 464.8 million. This meant that China's official population estimate, currently at 1.38 billion, was wrong, Yi said. Instead it should have been 90 million lower — a gap roughly the same as Germany and Belgium's population combined.

That would make it 1.29 billion, and lower than India's estimated 1.32 billion population, according to Yi.

Multiple media outlets in China, India and beyond quickly picked up the news. If Yi was right, the implications would certainly be big. Not only would it mean that India had already overtaken China as the world's largest nation — something the United Nations had estimated to happen in 2022 — but that China's population growth slowdown was worse than many thought and being hidden from the public.

Reached via email, Yi said the controversy was “no surprise” to him, but added that he had already noted his belief that China's official estimates were wrong in the 2013 edition of his book, “Big Country with an Empty Nest,” which took a critical look at China's family-planning policies.

In fact, Yi says he was sure the estimates were wrong far earlier. “In 2003, I knew China official announcement population data is much higher than the real population,” Yi wrote from Taiyuan, China.

Among the many notable elements of Yi's claim is where he's making it from: mainland China.

The academic, born in Hunan province, had moved to the United States in 1999. After moving to take up graduate studies at the University of Minnesota-Twin Cities (he later worked as a fellow at the Medical College of Wisconsin and moved on to the University of Wisconsin Madison as a scientist in 2002), Yi quickly became a vocal critic of China's family-planning policies, including its “one-child” rule.

In his writings, Yi suggested that these policies were limiting China's economic growth, meaning it could never compete with the United States. He also suggested that China could soon have a negative birthrate and a declining population, like its neighbor Japan.

Yi, who remains a Chinese citizen, claimed that his views brought him into conflict with the Chinese state. “Big Country with an Empty Nest,” first published in 2007, was initially banned in mainland China. He later told the New York Times that he was warned in 2010 he faced arrest if he returned home after helping his sister-in-law escape a state-ordered forced abortion.

China seemed to acquiesce to at least some of his arguments in 2015, when it abandoned the “one-child” policy and allowed all couples to have two children. Last year, Yi returned to China as a guest, but just a few months later his social media accounts were shut down — which he saw as a futile attempt at censorship.

Yi's status as a passionate activist against China's family planning policies is well-known and has led some to question his estimates of China's population.

Wang Feng, a demographer from the University of California, Irvine, expressed extreme skepticism of Yi's estimate. "Yi's conclusion is based on a very sloppy and overly simplistic assumption: that the officially published Chinese numbers overstated the number of births by a wide margin," Wang said, arguing that the birth censuses which Yi appears to have based his prediction on had their own problem of undercounting.

"Serious scholars have analyzed the census and other data and have made adjustment, unlike him," Wang added.

But according to the South China Morning Post, a number of other academics at Monday's Peking University Event seemed to concur that the government figures were off. “The government has overestimated the birthrate and underestimated the speed of demographic changes,” Li Jianxin, a demographer at Peking University was quoted as saying.

Yong Cai, a demography expert at the University of North Carolina, Chapel Hill, said he too disagreed with Yi's estimate and thought official statistics were closer to the truth. However, Yong said the fact that people were talking seriously about Chinese government data represented a major shift.

"Although Yi's estimate is erroneous, the public attention on it reflects an important change in Chinese society," Yong wrote in an e-mail. "The government no longer has the monopoly on information."

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