The new family planning policy allowing all couples to have two children took effect on Jan 1, but the number of newborns this year has been less than expected. The total number of newborns is expected to be just over 17.5 million, which is only 950,000 more than the 16.55 million in 2015, and 630,000 more than the 16.87 million in 2014.

The estimated number of newborns as a result of the new family planning policy accounts for 24 percent of the births in 2016. Given that about 90 million couples are eligible to have a second child, the actual number of second-born children will account for only 1 percent of the newborns in 2016.

The general trend in China is one of a gradual decline in the total fertility rate, and the continuous low birth rate has become a new demographic normal. According to the national sample survey in 2015, which covered 1 percent of China's population, the total fertility rate has declined to as low as 1.05.

After the previous change in the family planning policy - which allowed couples to have two children if either of them was the only child of their parents - gradually took effect in 2014, there was no baby-boom as some people had feared. Of the 11 million eligible couples according to the previous policy, only 920,000 applied by the end of 2014 to have a second child; the figure increased to 1.39 million by May 2015.

The figures show an overwhelming majority of Chinese couples may not be interested in having a second child. And the factors responsible for that - such as strict birth control in the past decades, low fertility desire and the huge cost of raising children - have left China staring at a low fertility rate trap.

Chinese people's fertility rate is generally between 1.6 to 1.8, which means the policy that allows all couples to have two children is not likely to achieve its goal. Given the rising living and housing costs, couples in general delay the decision to have even their first child, with many not even thinking of having a second child.

In other words, couples who desire to have two children comprise just a small percentage of all the childbearing-age couples, and those who truly have a second child are much fewer than those who have the desire to do so. The policy-made fertility rate is about 1.8, the wanted fertility rate is less than 1.5 and the actual fertility rate is less than 1.3.

Although the number of newborns is expected to increase in the short term, the fertility and birth rates will remain low. For instance, in East China's Zhejiang province, 152,000 couples eligible to have a second child according to the previous family planning policy had applied by the end of 2015 to do so. But they accounted for just about 20 percent of all the eligible couples in the province.

In the long run, the number of newborns relative to China's total population will remarkably decrease because of the low birth rate, as the number of women of childbearing age declines. In the decade from 2015 to 2025, the population of women between 24 to 29 years old, considered ideal childbearing age, will decline from 73.87 million to 41.16 million. This means the number of newborns will decrease by a half even if the fertility rate remains unchanged in the next decade.

In the next few decades, therefore, China will face the challenge of shrinking and aging population.

The author is a professor at the Population Research Institute of Peking University.