We can approach a very important demographic concept by way of Cavett’s Iron Law of Population.  Formulated many years ago by a man named Dick Cavett, Cavett’s Law articulates a basic truth: “If your parent’s never had any children, chances are you won’t either.”

Dick Cavett, obviously, was a comedian.   But his observation is not just funny. It’s also importantly true. Because, as a careful analysis will demonstrate, the ongoing global decline in human birthrates is the single force that will most affect the fate of nations and the future of society in the 21st century.

Some might regard that prediction as implausible.  After all, most of us just take it for granted that there will always be more and more people in the world.

We see it in our day-to-day lives. Every year, traffic gets worse.  Every year, the price of waterfront property gets more prohibitive.   If we turn on the television, we see images of Third World famine, war, and environmental degradation.  And we see a pattern of population growth in the official numbers (see graph: “World Population Growth”).

 Today, world population is increasing by some 76 million annually. That’s equivalent to adding a whole new country the size of Egypt every year. In my parents’ lifetime, world population has tripled.  Just during the 50 years since I was born, world population has more than doubled.

We have grown up—and continue to live in—an era of explosive world population growth. And for most of us, this phenomenon deeply informs our world views and expectations for the future.

But now, here’s a curious fact—the first of many essential to understanding our current demographic circumstance—world population is still growing, but the world supply of children is shrinking.

The claim that global population is growing while the number of children is declining may strain credulity.   But it’s true. This paradoxical trend started in Europe in the middle of the last century. Today there are 36 percent fewer children under age 5 in Europe than there were in 1960.   In Poland, the number of young children declined by a full 50 percent during this period.

Now that same trend is going global. For the world as a whole, the absolute number of children aged 0 to 4 is actually six million lower today than it was in 1990.

How can this be? Where have all the children gone?

To be sure, war, hunger, and disease still carry away millions of the world’s children. In parts of Africa, as many as 20 children die for every 100 that are born.

But as horrible as this reality is, it’s not the explanation for the shrinking supply of children. Child and infant mortality are generally improving throughout the world, often dramatically.  What has changed is something much bigger and newer and stranger.

It’s happening in rich countries. It’s happening in poor countries. It’s happening in Catholic countries; it’s happening in Protestant countries. It’s happening in Muslim countries, both Shia and Sunni. It’s happening throughout the Eastern Hemisphere and the Western Hemisphere, North and South. It’s happening under all forms of government.

And just what is this big, universal trend? More and more people are choosing to have only one child—or none at all. Birthrates are plummeting around the world.

Recent data indicate that among the major industrialized countries, only the United States still comes close to producing enough children to replace its population.  (See chart: “Fertility in Developed Countries”.)  In modern societies such as the United States, Japan, and Italy, the average woman must give birth to an average of 2.1 children in order to avoid long-term population loss.

Why 2.1?  To maintain a stable population, each woman needs to have one child to replace herself. Then she has to have another child to replace her male partner. Since some children die before reaching reproductive age, an additional one-tenth of a child is needed on average in modern countries to replace the population.

And yet there are fewer and fewer places left on earth where women still have as many as 2.1 children.  From Argentina to Austria, from China to the Czech Republic, sub-replacement fertility rates are now spreading to every corner of the globe.

True, the total fertility rate runs above 2.1 births per woman through most African countries.  But the AIDS epidemic in Africa and the high infant-mortality rates found through much of sub-Saharan Africa means that many of the countries in this region are actually experiencing below-replacement fertility levels.  South Africa, for example, with a total fertility rate of just 2.24 children per woman, is surely at below replacement level, given its high rates of child mortality.

Where is fertility falling the fastest? Just where most people think it is growing the most: that is, in the Middle East.  Consider, for instance, Iran’s little-noticed birth dearth. Who would know, from reading today’s headlines, that Iran’s total fertility rate fell below replacement level in 1999 and—according to the U.S. Census Bureau’s International Data Base—has since dropped to just over 1.6 lifetime births per Iranian woman, 22 percent below replacement level. Similarly, how many Americans know that Iran has been joined by four other countries in the region—Tunisia, Algeria, Lebanon, and Turkey—in the slide into sub-replacement fertility?  (See chart: “Sub-Replacement Fertility North Africa and the Middle East.”)

Most countries in the Middle East, to be sure, still have birthrates above replacement levels, and the populations are still growing.  But everywhere birthrates are falling, and the long-term trend is unmistakable. Even in Egypt, for instance, a country feeling the growing appeal of radical Islam, with its emphasis on patriarchy and pronatalism, total fertility has fallen from approximately seven lifetime births per Egyptian woman in the middle of the twentieth century to just three births in the early twenty-first century, with population scholars predicting a drop to sub-replacement fertility by mid century.  (See graph: “Lifetime Births Per Woman in Egypt.”)

A similar picture emerges in United Nations’ demographic data for Pakistan during the same period, where total fertility has fallen from over six births per Pakistani woman in the 1950s to just three births in 2000, with demographers again anticipating a continued slide to just two births by mid-century.

The same pattern, often even more striking, is evident throughout most of Asia, as recent demographic data make clear.  (See table: “Sub-Replacement Fertility in Asia.”)

In China, Taiwan, Japan and South Korea, birthrates have dropped so low that we see the emergence of so-called 4-2-1 societies: these are societies in which single child families are the norm, and each only child eventually becomes responsible for supporting two parents and four grandparents.

Despite the images Americans see in the media of China’s teeming cities, its working-aged population is on course to begin shrinking within ten years.  The big question for China is, Will it get rich before it grows old (as the West did), or will it grow old before it gets rich?

India is not yet on this list. As a whole, it still has an average fertility of about 2.5. But its southern provinces are already reproducing at well below replacement levels.

Sub-replacement fertility prevails in Eastern Europe as well. (See chart: “Sub-Replacement Fertility in Eastern Europe.”)

In a country such as the Czech Republic, fewer and fewer children have any siblings. If current trends continue, it will also be rare in another generation for anyone to have an aunt or an uncle. Similarly, nieces, nephews, and cousins are becoming endangered social species.

The retreat from childbearing is especially dramatic in the former Soviet Union. (See chart: “Sub-Replacement Fertility in the Former Soviet Union.”)  As a consequence of its plummeting birthrates and its very high death rate, Russia has a population that is shrinking by some three-quarters of a million people a year.

What about the United States? Within North America today, we see much the same pattern that we see in the world as a whole. That is, fertility rates are falling, and falling especially fast among historically disadvantaged groups.

Indeed, recent fertility data reveal that the only major American ethnic or racial group that has experienced an increase in fertility since 1990 is non-Hispanic Whites, and that increase has been a mere one percent. (See chart: “Change in Total Fertility Rates for Major American Ethnic and Racial Groups, 1990-2002.”)

Families are also shrinking among our friends to the south.  Indeed, the drop in the number of Mexican children is a national phenomenon without precedent in its speed and extent.  The number of Mexican children below the age of four has fallen dramatically—by tens of thousands—just since 1995!  (See graph: “Mexican Children, Age 0-4.”)

Informed observers see much the same picture elsewhere in the Americas.  Today, the median age in Latin America and the Caribbean may be 10 years lower than it is in the U.S.  But reliable UN projections indicate that the age gap will soon begin closing and will virtually disappear by mid-century.  The gap will close particularly rapidly if—as seems quite possible—the UN’s “low variant” projection for the region’s future fertility rates proves more accurate than the “medium variant” projection.  (See chart: “Shrinking Youth Supply to the South.”)  Since youthful Latinos are those most likely to immigrate to the United States, rates of immigration from South to North America may well taper off in the decades ahead.

Nonspecialists may understandably wonder how the population can continue to grow in countries where fertility rates are well below replacement levels. This perplexity can be resolved by taking into account the high rates of population growth that occurred in the ’70s and ’80s.  This population growth wasn’t the result of high birthrates, but of falling death rates, particularly for the children in the Third World.  And today, that accomplishment leaves a large percentage of the population still in its prime reproductive years.

But the demographic momentum traceable to the Seventies-and-Eighties population surge is fast dwindling. In many countries, such as Italy and Spain, population momentum has already turned negative. That is to say, in these countries the decades-long decline in the number of women of childbearing has created aging societies certain to shrink in the years ahead. Today in Italy, there are only half as many women of childbearing age as there were in 1960. A country in which women of childbearing age are disappearing is a society headed toward long-term depopulation. After a certain point, even if the average woman starts having substantially more children than her mother did, the population will still fall.

The dynamics that push society toward depopulation create another curious feature of early 21st century demography—something mankind has never seen before.  Never before has the world seen the global population continue to grow when almost all of that growth is among people who have already been born. Such a growth pattern defies traditional logic. But it’s quite real.

As already noted, the global number of small children is already falling. By 2050, according to one United Nation projection, there will be 248 million fewer children under age 5 in the world than there are today—even if birthrates rise in the developed world! But the population of elders will have swollen by nearly a billion. (See chart: “Total Fertility From Now On, Population Growth Comes From More Elders and Middle Aged People, Not From More Infants.”) Over the next half century, then, population growth will thus reflect the replacement of a smaller aging generation by a larger aging generation:  that is, population growth will come from people who are already alive, not the birth of new babies—as paradoxical as that might seem.

How sure the trend?  

But what is driving these trends, and how likely are they to continue?  In developed countries, sheer economics largely accounts for the disappearance of children.  In today’s advanced economies, many people are not even done with school before their fertility (or their partner’s) begins to decline.

Then there is the rising cost of raising children. In the U.S., the direct cost of raising a middle-class child born this year through age 18, according to government estimates, exceeds $200,000—not including the cost of college tuition. As women, as well as men, have gained new economic opportunities, the real cost of children in the form of foregone wages and compromised careers can often run much, much higher. Indeed in my book, The Empty Cradle, I calculate that, for a typical middle-class couple, the opportunity cost of raising a child just through age 18 can easily surpass $1 million—again, not including the cost of college tuition.

Meanwhile, although the world’s social security systems—and private pension plans—depend on the human capital created by childbearing parents, these systems create huge incentives to remain childless. We no longer must have children to find support in old age. Instead, we can rely on retirement benefits paid for by other people’s children.

Urbanization counts as another potent cultural development driving down fertility. As mega-cities have grown around the world, the percentage of the world’s population living in urban areas has grown from less than thirty percent in 1950 to over fifty percent in 2005.  This trend shows no sign of abating. UN demographers anticipate that by 2030 fully sixty percent of the earth’s population will live in urban areas.

The widespread use of safe and effective contraception and abortion also pushes fertility lower. Today, among married or cohabiting women of reproductive age, slightly more than 50 percent are using modern contraceptive methods.  Such levels of contraceptive use are found in rich and poor countries alike.

But a full understanding of current population patterns requires a careful look at the subjective—but perhaps more important—question of how sub-replacement fertility reflects  certain cultural and religious values (“memes” in the vocabulary of Richard Dawkins). Scholars who have scrutinized polling data have limned a strong correlation between what we might call modern, individualistic, secular values on the one hand and low fertility on the other.

Survey sociologists have identified a number of value questions that separate those inclined to have large families from those inclined to minimize or altogether avoid parental responsibilities.  For example, Do you distrust the army? Among Europeans, at least, those who say they do are far less likely to be married and have children, or ever to get married and have children, than those who do trust the military.

Do you think the most important goal in education is that of developing imagination and independence? Then according to polling data, there’s little chance you’ll have a large family.

Or again, are you not very proud of your nationality? Do you have little identification with the village or town you grew up in?

Do you find soft drugs acceptable?  Homosexuality? Suicide and euthanasia?  For whatever reason, people answering affirmatively to such questions are far more likely to live in childless, cohabitating unions than those who answer negatively.  (See table: “Anti-Natal Memes: Some values and attitudes associated with low fertility.”)

A variety of other modern attitudes also go hand-in-hand with low fertility. In Brazil, for example, birthrates have dropped, province by province, coincident with the introduction of television. Today, the more hours that a Brazilian woman spends watching television, the less likely she is to have a large family.

What’s on Brazilian television? Mostly domestically produced soap operas, called telenovelas. These soaps rarely address reproductive issues directly. Instead, they typically depict wealthy individuals living the high life in big cities.

The men are dashing, lustful, power hungry, and unattached.  The women are lithesome, manipulative, independent, and in control of their own bodies. The few who have young children delegate their care to nannies.

The telenovelas thus reinforce a cultural message that is conveyed as well by many North American and European cultural exports: people with wealth and sophistication are people who have at most one or two children.

Implications  

Sub-replacement fertility is a pervasive global reality. But what are the implications of that reality? Should we laugh or cry, be thankful or wary?

Space does not here permit full consideration of the implications of sub-replacement fertility.  But one social consequence of current fertility trends does deserve attention.

This consequence comes to light when people ask a natural question: Won’t persistent, sub-replacement fertility lead to eventual extinction? If current trends continue, Europe’s population, for example, will just wither away. But sober analysis suggests that current trends will not continue indefinitely in Europe or the West in general, for a special reason.

In Asian countries such as Japan, nearly every one eventually marries and eventually has one child. In Europe, and the West in general, by contrast, there is far more diversity in reproductive behavior. In my generation of Americans, for example, nearly a fifth of us never had children, and another 17 percent had only one.

The high incidence of childless and single-child families in the West has one big implication many overlook. It means a very large proportion of what children are being born are being produced by a small subset of the current population. And who are the people who are still having large families today?

The stereotypical answer is poor people or dumb people or members of minority groups.  But the more accurate answer is deeply religious people.

To be sure, religious fundamentalists of all varieties are themselves having fewer children than in the past. But whether they be Mormons, Orthodox Jews, Islamic or Christian fundamentalists, or evangelicals, devout members of all these Abrahamic religions have on average far larger families than do the secular elements within their society.

In Europe, for example, the fertility differential between believers and non-believers has recently been estimated at 15 to 20 percent.   Though children born into religious families often do not become religious themselves, many do, especially if they themselves go on to have children.

But if, over several decades, many of the secular-minded choose not to have children, the faithful begin to inherit society by default. Total population may fall, perhaps for quite a while; but those who remain will be disproportionately committed to God and family.

Remember Cavitt’s law: If your parents never had children, chances are you won’t as well.

A corollary might be, If you forgot to have children, chances are your descendents won’t grow up to be secular humanists.

Remember, too, that other strong finding of sociology, which is also enshrined in European folklore: “The apple doesn’t fall far from the tree.”

This is the way of the world.

The broad sweep of human history offers many examples of peoples, or classes of peoples, who chose to avoid the costs of parenthood. Indeed, sub-replacement fertility is a recurring tendency of human civilization. Like today’s modern, well-fed nations, both ancient Greece and Rome, for example, eventually found that their elites had lost interest in the often-dreary chores of family life. Here is the Greek historian, Polybius, around 140 B.C, lamenting the fate of his country as it gave way to Roman domination:

In our time all Greece was visited by a dearth of children and general decay of population... This evil grew upon us rapidly, and without attracting attention, by our men becoming perverted to a passion for show and money and the pleasures of an idle life.

By the time of Caesar Augustus, birthrates among Roman nobles had fallen so low that the Emperor felt compelled to enact steep “bachelor taxes” and otherwise punish those who remained unwed and childless. Augustus explained in clear language his deep concern about the Roman rejection of parenthood:

We liberate slaves chiefly for the purpose of making out of them as many citizens as possible; we give our allies a share in the government that our numbers may increase: yet you, Romans of the original stock...are eager that your families and names at once shall perish with you.

Needless to say, such exhortations didn’t work. Divorce became rampant in Roman society; childlessness increasingly common. When cultural and economic conditions discourage parenthood, not even a dictator—and many have tried—can force people to go forth and multiply. Eventually, the sterile, secular noble families of Imperial Rome died off, and with them, their ancestors’ traditional Roman ideals.

But what was once the Roman Empire remained populated. Only the composition of the population changed. Nearly by default, it became comprised of new, highly patriarchal family units, hostile to the secular world and enjoined by faith either to go forth and multiply or join a monastery.  Sociologist Rodney Stark has shown that nearly all the spread of Christianity in late antiquity was the result of higher birthrates, and lower death rates, enjoyed by Christians.

With these changes came a Medieval Europe, but not the end of Europe, nor the end of Western Civilization. But secularism and individual freedom went into a long decline. This cycle in human history may be obnoxious to the enlightened, but it is still very much with us.