Shanghai's birth rate is the lowest in the world and China's is below the level needed to maintain a stable population, according to "Too Many People in China?" - a book questioning the nation's one-child policy.
Shanghai's total fertility rate is an extremely low 0.7, the authors say. Developed countries such as Japan and South Korea introduced policies to encourage births because their fertility rates had dropped to 1.2 and 1.3.
Fertility rate refers to the average number of children a woman will have over her lifetime.
"Compared with other big cities like Tokyo, New York and Hong Kong, the fertility rate in Shanghai is lower. Because of the high cost or raising a child and the pressure of work, many Shanghai couples eligible to have a second child don't want to have more children," said Wang Guixin of Fudan University's population research institute. "For such couples, the government should introduce favorable policies to encourage childbirth."
Officials from Shanghai Population and Family Planning Commission said yesterday that only the central government had the right to change the population policy and there was no indication of that at present.
The 2010 census showed a 30 percent drop in the number of young people over the past 20 years, and China should change its strict population policy to ensure the nation's sustainable development, say the authors.
In the book published earlier this week, Liang Jianzhang, a PhD in economics from Stanford University, and Li Jianxin, a Peking University sociology professor, analyzed the Chinese population based on population research at home and abroad.
The latest Chinese census showed the number of people below 14 was 16.6 percent of the population, a drop of 6.29 percentage points from 2000. Globally, the number of children under 14 made up 27 percent of the population.
The authors say that China will have too few newborn children in the years ahead, which it called an "alarming" trend in the nation's economic development and potential.
They said that young people were the main drivers of technical innovation and wealth creation. Innovative and creative activities will decline along with the drop in the youth population, and this will lead to a sluggish economy when development is in its later stages, they argued.
The world's fertility rate is 2.7, compared to China's 1.5. A fertility rate lower than 1.5 means that the next generation will have 30 percent fewer people than the previous one.
If China's fertility rate sticks at 1.5 or goes lower, the authors say, the nation's population will plunge to 500 million in 100 years and people under 15 will form less than 10 percent of the population. People over 65 will be 40 percent of the population, the authors say, quoting a population report issued by the United Nations in 2011.
Fudan's Wang said experts had different opinions on China's current population policy. It did have the benefit of avoiding the birth of 400 million people over the past 30 years, thus easing the pressure on limited resources and causing an estimated 20 percent less environmental pollution.
Currently, couples can have a second child if both spouses are from one-child families or if their first child has a non-inherited disease.
In some rural areas, couples are allowed to have a second child if their first is a girl.