IT'S coming soon to an editorial page near you, the hottest new demographic issue: the specter of population decline. The issue is now emerging because birthrates in nearly all Western countries are below the so-called replacement level. On average, each woman must bear 2.1 children for a generation to replace itself. If current rates were to continue, the average woman in the US would bear only 1.8 children, and eventually the United States population would decline. Even so, the US decline wouldn't occur until the middle of the next century because of the large number of women now of childbearing age - a legacy of the baby boom - and because of immigration.
In Western Europe, however, the time when numbers would begin to decline is nearer. In West Germany, it has already arrived. Most other Western European nations are still growing, but at current rates, population decline would set in soon after the turn of the century.
Although there is a long history of concern in Europe about ``depopulation,'' only recently has this issue attracted attention in the US. In the past year, however, several articles in magazines and newspapers have warned of the negative consequences of what has been called variously the ``birth dearth,'' the ``sparse generation,'' or even the ``depopulation bomb.''
The more tempered discussions address potential difficulties such as the following: How will a relatively smaller work force pay for social security and health care benefits for a large elderly population? With fewer children and more women at work, will the elderly be able to rely on support from their families, as many do today? Will there be a lack of dynamism in a population that isn't growing? Will opportunities for advancement be limited? Will the pace of technological innovation slow?
These are important concerns, the answers to which are far from clear. Unfortunately, a number of more alarmist articles are also appearing which warn that nothing less than the survival of Western society as we know it may be at stake. Some authors point to the higher birthrate in the Soviet Union and conclude that the US may be outnumbered and, ipso facto, gravely threatened by Soviet power in the 21st century. Or they look at the more substantial birthrates in the developing nations and conclude that Western democratic values may soon be swamped in a third-world sea.
But such fears are greatly exaggerated. Consider national security. In a nuclear age it is simplistic to equate security with the number of potential soldiers. Moreover, the growth in the Soviet population is occurring not among ethnic Russians, but among Central Asians of Islamic heritage. This transformation may be a decidedly mixed blessing for the leaders of the USSR, who may find that ethnic and cultural differences threaten internal cohesion.
It seems equally implausible to equate the vitality of Western culture with a fixed share of world population. Between 1950 and 1985, as Western values spread throughout the developing world, the West's share of total population declined from 26 to 15 percent. Why should a projected decline to about 9 percent 40 years hence make any difference?
The more alarmist arguments ignore the difficulty of projecting long-term population trends. In the US, for example, anxious population experts in the 1930s and 1940s unanimously predicted declines - and were completely taken aback by the postwar baby boom. Today we are just becoming aware of the costs of sustained below-replacement fertility, such as the difficulty of supporting the elderly. Long before our numbers decline, we may make the adjustments necessary to return birthrates to the replacement level.
In 1968, Paul Ehrlich began his influential book ``The Population Bomb'' with these words: ``The battle to feed all of humanity is over. In the 1970s the world will undergo famines - hundreds of millions of people are going to starve to death.'' Today this erroneous pronouncement serves as an excellent example of the conservative charge that '60s and '70s liberals often exaggerated the seriousness of social problems. There is a lesson here for those commentators, primarily of conservative bent, who would now warn of the grave dangers of current trends. To be sure, a balanced, restrained discussion of the consequences of low birthrates is useful and needed; but we ought to defuse the rhetoric about the depopulation bomb before the debate explodes.
Andrew Cherlin is a professor of Sociology at Johns Hopkins University in Baltimore.