Overpopulation is one of the world's great problems. Theodore H. White has been in China, which has about a quarter of the people of the globe, and reports his findings in the October issue of Reader's Digest. ''There are simply too many people,'' he says. The government has adopted a policy of one baby per family and is now trying to enforce it. He summarizes the uncertainties: ''Logic lies on the side of the government, but love lies on the side of the babies.'' He adds, ''If the population increases even at the present reduced rate China must starve or explode.''
On a somewhat smaller scale a population explosion is going on in America's neighbor, Mexico. The United States has its population growth pretty well under control. The natural increase (births over deaths) is about 0.7 percent each year; when immigrants are included (legal and estimated illegal), the figure is around 1.2 percent. Mexico's expansion, by contrast, is extraordinary. It is estimated at from 2.1 to 2.2 percent or more. Mexico is growing so fast that Mexico City will have a population of 28 million and will be the biggest city in the world in a few years. There aren't jobs for the newcomers; there is an enormous foreign debt; Mexican eyes turn across the loosely patrolled 2,000-mile border.
Leonard F. Chapman Jr., former immigration commissioner, estimated in 1976 that ''at least 250,000 to 500,000 (illegal immigrants) arrive each year.'' He said, ''They are milking the US taxpayer of $13 billion annually by taking away jobs from legal residents . . . by illegally acquiring welfare benefits and public services, by avoiding taxes.'' This figure is a guess. Some say 3 million Mexican illegals; others, 12 million. Nobody knows.
The slow-moving Congress seems to want to tighten the border defenses. But it goes against the grain. Doesn't the Statue of Liberty welcome all foreigners? Aren't we all descended from immigrants? Mexico is the source of 85 percent of the illegals. The United States had a military budget of $143.9 billion in 1980 to prevent armed invasion, but spent only $111 million trying to defend its borders against another kind of invasion. John J. Gilligan, head of the Agency for International Development in Boston, declared in April of 1978 that ''Mexico has the largest growth rate in the world,'' adding that ''because of lack of employment, 15 to 20 percent of the adult population of Mexico has crossed the border illegally and is at work in the US.''
After some years the slow-moving Congress has attempted to write legislation imposing fines and criminal penalties on employers who knowingly hire illegal aliens. One version of the bill, sponsored by Sen. Alan Simpson (R) of Wyoming, has passed the Senate and a second, by Rep. Romano Mazzoli (D) of Kentucky is scheduled for the House Rules Committee, Oct. 18. Congress always has difficulty with this kind of complex, controversial, and fundamental legislation. It would set up a kind of identity card for immigrants. Some Hispanic groups don't like it, and they have increasing votes. On the other hand, the Labor Department estimates there are 10,580,000 unemployed in America.
Will Congress finally act? This week House Speaker Thomas O'Neill suddenly said the measure would not be brought up this year. He complains of lack of support from the White House. If not passed in 1983 it seems unlikely to pass in '84 in a presidential election year. Something should be done. But Republicans control the Senate, Democrats the House, with the President of one party and the House Speaker of the other. The House Rules Committee may pass an amended version of the Mazzoli bill, but the Speaker must then decide whether to bring it to the floor; he has said that he will not. Meanwhile, every night over the Rio Grande illegals are wading across. Just last month (Sept. 22) Immigration Commissioner Alan C. Nelson told a press conference that the millionth would-be illegal had been intercepted and turned back. How many enter undetected?