China needs a baby boom—and badly, researchers say.

"Get married soon and have lots of children." That's the advice that 49-year-old Huang Wenzheng gave to college students at a recent forum in Beijing about China's population and urban policy.

Mr. Huang, one of the most outspoken one-child policy opponents in China, along with other activists and economists, said at the forum that China needs babies more urgently than ever before, and the country's economic fate depends on whether Beijing can do more to encourage child births.

A shirking population would be detrimental to China's development, "leading to a drop of China's national power and even a decline of the civilization," said Mr. Huang, a co-founder of the website Population and the Future, which promotes the right to have more than one child.

China's total population continues to grow, but the nation's working-age population—those between the ages of 16 and 59—has dropped two years in a row, raising concerns about a shrinking labor force and economic growth prospects. The share of the elderly, or those who are more than 65 years old, was 9.7% in 2013, up from 9.4% in 2012, official data showed.

A labor shortage in the short run would be followed by diminishing demand, which in the long run will likely hurt China's job market and decrease the number of jobs being created, said Mr. Huang, who received a PhD in biostatistics at John Hopkins University.

Such a message isn't falling on entirely deaf ears: late last year, Beijing moved to ease its decades-long one-child policy by allowing couples to have two children if one spouse is an only child.

But the policy's impact has been limited. By the end of May, only 271,600 couples had applied for permission to give birth to a second child, with 241,300 couples having been given the permit, Yang Wenzhuang, a director overseeing family planning at the National Health and Family Planning Commission, said at a briefing in July.

Economists and researchers say such small steps are far from enough.

"I've been traveling to different parts of the country in recent months to find out exactly what changes are taking place in our society…but wherever I go those who actually qualify [to have a second child] is less than 5%," said Gu Baochang, a professor at Renmin University. The reason why that figure is so low is in part because many rural residents were already permitted to have a second child. Likewise, China's rules previously allowed individuals who have no siblings to give birth to a second child, so long as they were married to someone who matched those same conditions.

Faced with a rapidly aging population and declining numbers of the working-age, government officials have strongly hinted that they may need to raise the retirement age.

The ratio between the number of people who are paying into the country's social insurance pool and those who receive pensions rose to 3.09 in 2012, up from 2.90 in 2003, the latest official data showed.

"When you are 60 years old, who would support you?" the silver-haired Mr. Gu said to an audience of about 400 students, researchers and journalists last week.

Results of the most recent census in 2010 showed that China's fertility rates, or the number of births per 1,000 women, was 1.18. Large cities and Beijing and Shanghai were even lower, at around 0.7.

As China's urbanization rate increases, with more farmers moving into the city, the fertility rate will drop further due to higher living costs, said Liang Jianzhang, a professor at Peking University.

To make it worse, China is seeing a rising number of "leftover women," or middle-aged urban Chinese women who cannot find their Mr. Right—and unlike single women in developed nations, unmarried Chinese woman are not willing to have children, said Mr. Liang, who's also the founder and chairman of Ctrip.com, Chinese online travel company.

"However you look at it, [the outlook of] China's fertility rate seems more pessimistic than a lot of other countries," he said, adding that in 10 to 20 years, China's population will be greying at a pace even faster than that of a decade ago in Japan, where the elderly currently make up 25% of all residents. An aging population has partly contributed to the "lost decade" of the Japanese economy, economists have said.

But others at the forum disputed the notion that China should be encouraging a new baby boom.

"Sounds like we are returning to Chairman Mao's line of thinking…I think we must not make that kind of mistake," said Chen Zhiwu, a Yale University professor.

Mr. Huang, however, said that even if the government completely scraps the one-child policy, the country's fertility rate still won't be 'normal,' and will instead continue to stay low.

"It would be disastrous for China," he said. "No doubt about that."

-- Liyan Qi

_____________________________________

Also popular on China Real Time now:

Back to the Drawing Board for Hong Kong Election Reform?

Beijing's Traffic is Going to Get Truly Awful Next Week, City Warns