China has succeeded in curbing its excessively rapid population growth and reducing its fertility rate through its rigid family planning policy over the past three decades. The population growth rate has dropped from 2.5 percent in 1960 to 0.5 percent nowadays, and the yearly average number of newborns has dropped from 27 million in the 1960s to 16 million now. Based on the current growth trend, China's population will step into a "zero growth" era in the 2030s. The changing population situation has drawn wide public attention to the adjustment of the family planning policy.

Under the influence of the family planning policy during the past three decades, China has accumulated 180 million to 190 million single children in their families, and the number of only children whose mothers are under the age of 50 is about 150 million. This means there are about 150 million couples where either the husband or the wife is the only child. By opening up the family planning policy to allow these families to have a second child, all these 150 million couples are immediately qualified to have a second child. Of course not all of these couples will want a second child. According to many national surveys, about 60 percent of couples say they would like a second child, which suggests there will be about 90 million newborn babies in the near future.

This accumulation effect will be gradually released in several years after the adjustment of the policy. Without restriction, Chinese women's average birth spacing is three to four years. It's estimated that women who have already given birth to a child will have another within about four years. If we suppose for the sake of argument that these women's birth timing will be uniformly distributed at four years, it can be estimated there will be an extra 22.5 million births every year in the following four years due to the releasing of accumulated childbirth power. Currently there are about 16 million newborns every year in China. And there will be about 40 million newborns ever year in the following four years now the policy has been relaxed.

However, this argument is unrealistic because the women who want to have a second child will not give birth to babies according to this theoretical timeline. Statistics show that the release of accumulated fertility power will peak in the third and fourth year. Under such circumstances, in the peak year there will be more than 40 million newborn babies in China, while China's highest yearly newborn population after the founding of New China has been 29 million.