If every woman of childbearing age in China has an average of three children, as was the case in 1975, China's population 100 years from now will approach that of the entire world today.
If, on the other hand, the current campaign for every couple to have only one child is successful, China's population, now nearly 1 billion, will decline to 370 million by 2080.
These startling contrasts are featured in an article in the Guangming Daily, a national newspaper oriented to intellectuals and professionals. Recently, the article said, for the first time a group of scientific workers in Peking made various projections of population growth in China over the next hundred years.
The article is part of the government's intensive campaign to encourage one-child families so as to reduce and eventually to eliminate the intolerable strains placed on the nation's economy and well-being by population growth. The rate of growth is already down to 1.2 percent per year. But even this rate, low for a developing country, adds at least 12 million people a year to China's population.
In a recent interview, population expert Liu Zheng of the People's University of China said that there was no way China could reach its goal of bringing down the growth rate to 0.5 percent by 1985 and zero by 2000 without making sure that by 1985 each couple had no more than one child per family.
But that requires some radical change in attitude here. Can the goal be achieved?
We have friends who are expecting their first baby. If it is a boy, they plan to have no more children. And if it's a girl? The prospective father, at least, is reluctant to say.
Mr. Liu blamed the lack of a consistent population-control policy in the 1950 s and 1960s, and especially the harsh criticism of respected economist Ma Yinchu in 1957, for China's inexorable population growth during this period.
Professor Ma wrote his famous treatise "New Population Theory" in 1957, when China's population was 656.63 million. In it he pointed out how birth control would accelerate economic growth, promote science and technology, and raise the material standards of peasants.
He was forced to resign as president of Peking University and population theory became a "forbidden zone," Mr. Liu said, even though population control itself remained a government policy. As a result, in the 20 years since Professor Ma's treatise, China's population has grown by half as much again.
The scientific workers cited in Guangming Daily carry the argument a step further. Their most horrific projection is that if every woman of childbearing age has an average of three children, by 2000 the population will soar to 1.414 billion excluding Taiwan. By 2050 the population will be 2.923 billion and by 2080 it will reach 4.26 billion.
Even if the average rate is brought down to two children per couple, the population will continue to increase for 72 years and peak at 1.539 billion in 2052, before beginning to decline slowly.
More drastic population restraint -- to an average of 1.5 children per couple -- would still mean a population of 1.125 billion in 2000, and a peak of 1.172 billion 2027.
As desirable as this projection may seem over the long term, population experts here still feel it is inadequate to curb population during the years when such curbs are most necessary -- the next two decades, during which all-out efforts must be made to achieve rapid economic growth and to raise standards of living.
Thus the campaign to get couples to promise to have but one child per family and to make this the rule by 1985. That, the scientific workers say, would mean population peaking at 1.054 billion as early as 2004, a return to the present level of 960 million by 2028, a decline to 613 million by 2060 and to 370 million by 2080. Even under this drastic policy, the population experts say, China does not have to worry about an aging population for several decades.
In 1978 and 4.8 percent of China's population was aged 65 or over, and by 2000 this percentage will reach only 8.9, whereas already in 1975 over 10 percent of the population in developed countries like the United States and East and West Germany was over age 65.