WHERE HAVE ALL THE BABIES GONE? A social theorist argues that falling birthrates in the U.S. will lead to the decline of the West.

(FORTUNE Magazine) – Twenty years ago, environmentalists warned that a population explosion threatened the planet. In his best-selling book, The Population Bomb, Paul Ehrlich predicted that the number of people in the Third World would double in 25 years, the U.S. population in 63 years. Declared Ehrlich: ''The birth rate must be brought into balance with the death rate or mankind will breed itself into oblivion.'' Implication: Anyone who had another child was to blame for famine, pollution, and the ultimate decimation of the human race.

What a difference two decades makes. Ben Wattenberg, a senior fellow at the American Enterprise Institute, has written an equally apocalyptic tract making exactly the opposite case. The Birth Dearth (Pharos Books, $16.95) argues that falling birthrates in the U.S. and other industrialized democracies are contributing to a Spenglerian decline of the West. Now Americans who don't have enough children are to blame for the impending demise of Western civilization. What disturbs Wattenberg is that American fertility rates have plunged 54% in 19 years -- from 3.77 to 1.74 births per woman. For the past ten years the rate has stayed at about 1.8 births per woman, well below the replacement level of 2.1. Fertility rates are even lower in Europe. West Germany (1.27) and Denmark (1.4) are losing population, and Italy, Switzerland, and the Netherlands (1.5) are in danger of doing so. Wattenberg quotes French Prime Minister Jacques Chirac's saying that ''Europe is vanishing.'' Fertility rates are falling in Eastern Europe and the Third World too -- but less rapidly. And despite declining fertility, these countries are still gaining population. They accounted for 78% of the world's population in 1950. Today they hold 85%, and Wattenberg expects them to contain 91% by 2025. The fertility rate in Eastern Europe, excluding the Soviet Union, is 2.1, 31% higher than the rate in Western Europe. The World Bank predicts the Eastern European population will grow from about 116 million today to 138 million in 2030. The Soviet Union averages 2.4 births per woman, thanks largely to its prolific Central Asian minorities. The World Bank says the Soviet population will grow by 100 million people in the next 100 years (an increase of 35%), while the U.S. adds 33 million, or 15%. The Soviets, says Wattenberg, will achieve ''victory in the bedroom.'' He figures that by the end of the next century there will be almost 600 million people in the 22 countries that make up what he calls the Western community -- and nearly 10 billion elsewhere. A decline in the growth of the Western population, Wattenberg argues, will force the economy to contract, producing fewer tax dollars that will buy less military power and global influence. ''In my judgment,'' he writes, ''the major threat to Western values and the free world concerns the fact that, as the next century progresses, there won't be many free Westerners around to protect and promote those values.'' In addition, he argues that a declining growth rate will cause economic turbulence as corporate America adjusts to the demographic changes, domestic tension as the white population declines, and personal misery as people go through life without children. To show how to avert these calamities, Wattenberg tries to identify which group has stopped procreating. It is not blacks, who have 2.2 children per woman, nor Hispanics (2.4), nor poor whites (2.1). Concludes Wattenberg: ''The Birth Dearth is due to low fertility among the white middle and upper middle class'' (his italics). White households earning between $20,000 and $25,000 have 1.7 children per woman. The rate for households with incomes over $35,000 is 1.3. Those figures substantiate a basic law of demographics: As family income goes up, fertility tends to decline. Since 1965 per capita income in the West has risen by 56% (after adjusting for inflation). Availability of birth control pills and legalized abortion has pushed fertility rates down further, as have such trends as later marriages and increasing tolerance of homosexuality. And as women of childbearing age enter the paid labor force, fertility goes way down. In 1940, when only 17% of married women were in the U.S. labor force, the fertility rate was 2.2. The rate has plummeted in part because 53% of women now work. FEW DEMOGRAPHERS dispute that the U.S. fertility rate is likely to stay low. Some even expect it to drop further. The problem is that demographic trends are volatile and difficult to predict. Demographers in the 1930s shared many of Wattenberg's worries. But their predictions went awry with the postwar baby boom, which none of them anticipated. Wattenberg's case is weakest when he assumes that current patterns will be permanent. For example, he overlooks the likelihood that Third World countries will gradually become more industrialized, which should cause their fertility rates to decline. Says Charles Westoff, director of the Office of Population Research in Princeton, New Jersey: ''Wattenberg's implication is that the existing differences will be unchanged. The premise is crazy because those differences are not going to continue unchanged.'' Another phenomenon that may dramatically alter current fertility patterns is AIDS. The threat of the disease could encourage Westerners to marry earlier, increasing the fertility rate. Moreover, AIDS is so prevalent in Africa that demographers believe it could devastate entire countries. Wattenberg, who argues that Africa is likely to contribute to huge increases in the Third World's population, devotes exactly two paragraphs of his book to the potential consequences of AIDS. He makes another mistake in his discussion of population growth and military strength when he equates strength and numbers. Numbers are of course only one component of military power. Industrial might is far more important. Some developed countries with small populations -- South Africa, to name one -- command considerable military muscle. China has millions of people but not much firepower.

Aside from making more babies, how might the U.S. increase its population? Immigration is an obvious answer. Wattenberg supports more immigration, but he doubts it is a long-term solution. ''The Statue of Liberty rhetoric notwithstanding,'' he writes, ''there has always been substantial public resistance to high immigration rates in the U.S.'' Furthermore, Wattenberg implies that there is a danger of admitting the wrong kinds of huddled masses. He notes that 80% of the U.S. population is of white European stock. At roughly current rates of fertility and immigration, the white European share will be down to 60% by 2080. The new immigrants -- Hispanics, Asians, Africans, and Arabs -- differ from the old European immigrants not only racially but also culturally, Wattenberg says. ''Will America remain a nation that can continue to be characterized as one that is predominately of white European extraction?'' he asks. Perhaps not. But his ethnocentric worrying fallaciously assumes that the U.S population must be of European (or established American) extraction to perpetuate Western values. That assumption is as unfounded as the fears of earlier generations that Italian, Irish, and Jewish immigrants would undermine American institutions. Immigrants are attracted to American values, not hostile to them. That is why they come to the U.S. Wattenberg concludes that demographic ''turbulence would be much less likely to show up if the real culprits, the non-reproducing white middle class, started reproducing itself.'' He devotes much of his book to lobbying readers to procreate, making comments like, ''What kind of spirit is there in a society that doesn't have the gumption or interest to reproduce itself?'' or ''There will be much personal misery if a quarter to a fifth of women have no children, if fertility is so low that four grandparents must share one grandchild . . . '' Finally, Wattenberg calls for a public campaign to persuade yuppies to change their ''me-oriented and self-actualizing'' spirit to recognize that only they can save civilization. IF HIS progeny propaganda is unpersuasive, Wattenberg is willing to ''buy babies'' through pro-natal policies. Here he makes Lyndon Johnson sound like David Stockman. ''Money should be no object,'' he declares. ''Remember, we're saving Western civilization.'' He advocates government-supported day care, changes in the tax code to encourage families to have more children, even bribing couples to bear children by providing a $2,000 annual check for 16 years for each child. While conceding that the latter would be ''a very expensive program, costing hundreds of billions of dollars over time,'' Wattenberg insists that ''nickel-and-dime programs usually don't work.'' The real flaw in his thinking is that he doesn't seriously attempt to weigh the costs of his policies against their tangible benefits. For example, he provides no clue as to how much the government would need to spend to increase births a given amount. Nor does he seem to realize that lawmakers who hand out fat subsidies for every child a couple produces will be enriching quite a few people who would have had children without a bribe. Wattenberg has given readers a superficial and hysterical glimpse of a manageable population problem. His book is as speculative as The Population Bomb. We learned from the last population scare that while demographic horror gurus sell lots of books, they usually predict the future with about as much accuracy as a reader of tarot cards.