BEIJING — Eight thousand miles is a long way to fly someone so he can tell you you're wrong.
That's what awaits Chinese officials on Friday when Yi Fuxian, a scientist at the University of Wisconsin-Madison, speaks at a panel on China's population policies at the Boao Forum, an annual gathering of hundreds of politicians, businesspeople, opinion leaders and journalists.
这正是中国官员周五要做的事。届时，威斯康星大学麦迪逊分校(University of Wisconsin-Madison)的科学家易富贤将在博鳌论坛的一场专家讨论中，谈论中国的人口政策。博鳌亚洲论坛每年召开，有数以百计的政商人士、意见领袖和记者参加。
The day will mark a remarkable transition for Dr. Yi, from pariah to V.I.P. Six years ago, officials in his home province of Hunan threatened to arrest him if he returned from the United States, where he has lived since 1999, for helping his sister-in-law escape a forced abortion at seven months, he said in an interview in Beijing this week en route to the forum in Hainan Province. Also, his cousin's wife's baby was killed in utero one week before the baby's expected birth, he said. It was not possible to confirm Dr. Yi's accounts, but they echo many confirmed ones.
Dr. Yi has a message for Boao: Because of China's birth control policies beginning in 1980, there is no way its economy will overtake that of the United States. Growth is already beginning to fall amid a distorted demographic structure, he said.
After the 1949 revolution, "we had the advantages of having lots of young people," said Dr. Yi, who remains a Chinese citizen. "But that's ending."
"People say we can be two to three times the size of America's economy," Dr. Yi said. "I say it's totally impossible. It will never overtake America's, because of the decrease in the labor force and the ageing of the population." The United States has a much healthier age distribution, he said.
Sharing this concern, last year the government increased the number of permitted children, from one for most couples, to two.
It won't help, said Dr. Yi, a medical researcher, father of three and author of the 2007 book "Big Country With an Empty Nest," which criticized the birth policies and was banned in mainland China until 2013.
As the number of women of childbearing age shrinks, so will births in a long-term trend, he said. Meanwhile, a rising median age is creating great financial burdens.
Dr. Yi creates scores of graphs using data from the government's national population censuses and its "one-percent" mini-censuses. He pieces official figures together as they are released in snippets, updating constantly. The projections are his own, he said.
In 2013, the government had already relaxed its policy to allow couples in which one partner was a single child to have two children, expecting a rise in births.
Instead, there were 320,000 fewer births in 2015 than in 2014, bolstering his point that it was too little, too late, Dr. Yi said.
"The 2015 one-percent census will show that fertility in 2014 was 1.25 children per woman," he predicted. "They expected 1.8."
"Now they say with two kids, they'll get 2.1 children per woman," Dr. Yi said. "But they won't. I think they'll get 1.4. Over all, they say they'll get 21 million births per year. I don't think so. Maybe 15 million."
He sees China's population, now at 1.35 billion, declining.
"By 2060 there will be one billion Chinese. By 2080 there will be 700 million. And the result will be — all old people," he said, flicking through graphs for a lecture he will deliver at universities across the country in April, after Boao. He predicts that within two years the government will have to lift all birth restrictions.
The world has grown accustomed to hearing from Western and Chinese economists and businesspeople that China's economy will overtake that of the United States in 2025, or in 2030 or another point in the future. That makes Dr. Yi's message one that will be hotly debated, including by China's leaders, who only partly understand, he said.
"They're not as worried as I am, because they haven't fully understood the problem yet," he said.
"I can go to Boao because the Chinese government isn't against me anymore!" he said. "Before, they said I was a traitor because I opposed state birth policies. Where I used to be a traitor, I'm now being paid to fly, business class, from Madison to Chicago, to Beijing, to Hainan."