And if fertility rate stays the same, the total population will peak at approximately 1.5 billion around 2033; and China's working-age and elderly population will peak in the first half of the 21st century, said China's first National Population Development Strategy Research Report, released in 2007.

As the population grows, the amount of resources available to each person dwindles. Currently, China ranks 120th in the world in the resources available to each person, with per-capita cultivated land, water resources and mineral resources at one-third, one-fourth and one-half the global average, respectively, according to statistics cited by China Economic Weekly.

A large population also puts more pressure on the nation's food supplies, job market and the environment.

Quickly controlling and reducing the country's population will improve citizens' lives and shrink the gap between China and the Western countries in terms of per-capita GDP and living standards, said Cheng Enfu. He added that scientific and rational population-control policies will create economic and health benefits and promote the harmonious development of the society.

Cheng was strongly against the idea of allowing a couple to have two children. The average Chinese family has to spend at least tens of thousands of yuan per child from the mother's pregnancy to the 16th birthday, he said. The cost of raising children will increase over time, and more offspring would consume more resources, placing a heavier economic burden on the families and the society, Cheng said.

Statistics cited in China Economic Weekly show that a two-child-per-family policy would add 863 million Chinese by 2100.

Policy debate

The current one-child policy has negative impacts on a child's psychological health, said Ye, when he called for a policy change during the 2007 CPPCC session. As the only child in the family has neither brothers nor sisters, it can lead to personality problems and subject an individual to the heavy burden of supporting elderly family members, Ye added.

The one-child policy has created two social problems, according to Ji. The first problem is the abnormal gender ratio created when parents prefer male to female. Ji said the third census conducted in 1982 showed that the male to female ratio in China to be 108.5, whereas in 2007, official statistics showed the ratio to be as high as 120.2. Ji said the normal ratio should be 107.

The second problem is population aging. The percentage of people above 65 years old increased from 4.9 percent in 1982 to 7.6 percent in 2005, Ji said. If the current family planning policy continues, the elderly would account for 28.4 percent of the total population in 2026, Ji added, and such a large senior population would be a burden on both families and society.

Mu said the one-child policy also held many potential risk factors for families. For instance, the only child's premature death or grave illness can be catastrophic for middle-aged or senior parents. As the sole children tend to be pampered by parents, they might not live up to their expectations and become a burden rather than a help to their parents.

As the fertility rate has remained low and stable, China should adjust its population policy from population control to population optimization and from seeking negative population growth to seeking balanced growth, said Mu. The family planning policy should become more lenient, he said, and a balance should be found between the interests of the nation and those of the family.

Wang Guoqiang, former Vice Minister of the NPFPC, said the one-child policy is often a misnomer when talking about the actual number of children Chinese families are allowed. Wang pointed to statistics that showed that under the current policy, only 35.9 percent of Chinese couples were not allowed to bear more than one child. In the rural areas of 19 provinces, Wang said, a couple whose first child is a girl can give birth to one more child, and in the rural areas of five provinces or regions, two children are allowed for each couple. In some areas like Tibet, there is no restriction on the number of children a minority ethnic couple can have.

Wide disparity between regions across China makes a one-size-fits-all policy unfeasible, NPFPC's Zhang said. He held that any population policy must take into consideration those regional differences, and the family planning can only be adjusted gradually if necessary.