In 1978, Song Jian, Tian Xueyuan and others calculated that China's population would reach 4.264 billion by 2080 and proposed a population cap of 650 to 700 million
In 1978, after missile expert Song Jian went abroad for exchanges, he and Tian Xueyuan and others used mathematical models to calculate, claiming that if China did not control its population, it would reach 4.264 billion by 2080; Tian Xueyuan also proposed that China's population ceiling should be 650 million to 700 million, providing a basis for family planning.