This past year, fertility rates in the United States fell to a historic low, with the Total Fertility Rate (TFR) standing at 1.7 (that statistic refers to the number of children a typical woman will bear during her lifetime). Technically, the present U.S. figure is known as a sub-replacement rate, as it is well below the number needed for a population to replace and maintain itself indefinitely, which is 2.1. Such a precipitous fertility drop has sweeping implications, especially as it has occurred in such a short period—just in the past decade or so—and recent changes have attracted intense attention from economists, planners, and politicians.

As yet, however, observers of U.S. religion have shown little concern or interest—which is curious since, worldwide, a move to very low fertility has been an excellent predictor of secularization and the decline of institutional religion. Fertility and faith travel closely together. Present demographic trends in the United States are the best indicator yet of an impending secular shift of historic proportions, even a transition to West European conditions. This is, or should be, one of the most significant and newsworthy developments in modern American religion.

European Precedent

That European precedent demands our attention. In the 1950s, European rates ran at high baby-boom rates, around 3.0 children per woman, or more. From the mid-1960s, sharp falls became evident, first in Protestant countries—notably in Scandinavia—and then in Catholic lands. By the 1980s, some European countries were pushing rates to unprecedented lows of 1.3 or lower, although they have subsequently rebounded somewhat. A typical European country today has a TFR around 1.7 to 1.8—roughly equal to the United States.

That fertility drop coincided perfectly with a well-known and much-studied move away from institutional religion, which in some countries amounted to something like evaporation. That drop also coincided with a tectonic shift in public morality, as referenda resulted in the legalization of once unthinkable innovations: the legalization of contraception, abortion, same-sex marriage, and euthanasia.

Present demographic trends in the United States are the best indicator yet of an impending secular shift of historic proportions.

Reeling from repeated defeats, the churches suffered a disastrous fall in their prestige and popularity. By all standard measures—church attendance, clerical vocations, even a willingness to identify as Christian—many European countries became radically secularized.

Understanding the Connection

To say two trends coincided doesn’t necessarily imply they’re connected; anyone who’s ever taken an introductory statistics course knows about the problems of distinguishing between correlation and causation. Still, the European experience does strongly suggest an intimate linkage between fertility and faith, although we can argue about the direction of change.

One path of explanation suggests that first religiosity decline, which then leads to declining fertility and smaller families. As is commonly noted, larger families tend to be more connected to religious institutions, and more committed to religious practice. Perhaps conservative and traditionalist believers tend to be more family-oriented, more committed to continuity and posterity, and thus they have more children; or else people in large families tend to be more conservative, more vested in traditional religious faith.

Multiple long-term studies point to such a correlation. Indeed, the association between conservative or traditionalist religion and high fertility is often used to explain the relative success of conservative denominations in modern U.S. history, at the expense of liberal mainliners. What separates the winners and losers in the religious economy, some say, isn’t the soundness of their theology, but their fertility rates. But now let us imagine conditions changing so that levels of religious belief decline, and the number of people with no religion grows—then we would expect a consequent fall in fertility.

This is, or should be, one of the most significant and newsworthy developments in modern American religion.

Alternatively, we might suggest that fertility declines first, and that this decline affects religiosity. Smaller families reduce their ties to organized religious institutions, as there are simply fewer children to put through religious school and First Communion classes, or the equivalent training and socialization in other religions. As religious ties diminish, ordinary people increasingly define their values in individualistic and secular terms, and are more willing to oppose churches or religious institutions on social and political issues of gender and morality. In part, this opposition results from the growing separation between sexuality and reproduction.

But it’s scarcely necessary to determine an exact sequence of change, since the two factors—fertility and religiosity—work so closely together and developments occur within a short time span. We might imagine a community that becomes increasingly detached from traditional religious-based concepts of gender roles. That reduces the ideological pressure to define one’s role in terms of family, parenthood, and posterity. As women become emancipated from familiar roles, they become more deeply involved in the workforce, and don’t have time for the large families of their mothers’ generation. That change in turn reduces ties to religious institutions. A shift to lower fertility encourages declining religiosity, which in turn discourages religious enthusiasm, and so on, in a kind of feedback loop. These two factors—family size and religiosity—work intimately together in ways difficult to disentangle.

I must draw one critical distinction. We often talk loosely about “secularization,” but in fact that word covers two distinct trends or currents. Scholar Grace Davie wrote acutely of the two patterns of religious believing and belonging, which are often associated but not inevitably. What has changed most spectacularly in modern Europe is the declining willingness to belong to religious institutions and to participate in their life. At the same time, many Europeans who no longer attend churches still show every sign of believing and of following private kinds of religion with some enthusiasm. Christian pilgrimage, especially, remains as popular as ever before. With that caveat, organizational and institutional religion are in crisis.

Global Change

For some years, social scientists noted the twin revolutions underway in Europe—the demographic and the secularizing—and assumed that these were specific to European conditions. But it soon became apparent that Europe was a pioneer of a much wider global change, which since the 1970s has transformed much of the globe. Since 1970, Mexico’s TFR has fallen from almost 7 children per woman to 2.2—in other words, to just above replacement. In the same years, Vietnam’s rate fell from 6.4 to 1.9, Indonesia’s from 5.4 to 2.3, India’s from 5.5 to 2.3. South Korea’s fell quite sensationally from 4.5 to less than 1.0, which is one of the lowest figures on the planet. The change is still more marked in some regions within countries. Around half the states of India presently have TFRs below replacement, and such populous and influential states as Punjab and West Bengal have fertility rates below Denmark’s.

Most observers think these recent plunges will continue over the next decade or two, to spread something like what are presently German or Italian demographic conditions around much of the non-European world. In a recent book, John Ibbitson and Darrell Bricker imaginatively surveyed the long-term effects of demographic decline and population contraction. The chilling title of their work: Empty Planet.

But if European-style demographic patterns have reached so much of the world, surely the religious picture can’t have changed so much? Actually, that correlation appears in many countries separated by thousands of miles. As fertility rates have collapsed across much of Latin America, so has the level of religious involvement and participation—of belonging. Meanwhile, surveys show significant shares of the population reporting membership in no denomination or religion, and who are thus counted as “Nones.” As in Europe, the declining power of churches, whether Protestant or Catholic, is reflected in the spread of liberal legislation in sexual morality; and again, same-sex marriage offers a valuable barometer. Until recently, several Latin American countries were actually much more liberal in these matters than the United States.

East Asian countries present a similar picture, which has affected non-Christian faiths. Witness the calamitous situation of Buddhism in most of its low-fertility Asian heartlands, such as Japan, Korea, or Thailand. Look at Japan, where so many temples face closure in the next decade or two. Even among those who identify as Buddhist, the degree of involvement in formal religious activities has plummeted in recent decades, so that few Japanese Buddhists ever have contact with a temple. Buddhist priests are well aware they are largely of the older generation, offering little appeal to the young, although some younger clerics try to repackage their message in trendy contemporary forms. Japan simply no longer has the cohorts of young men who might once have flocked into the monasteries. At every stage of this story, analogies to Europe’s Catholics or Anglicans or Lutherans are obvious.

By 2050, people of African origin could constitute a third of the world’s Christians, perhaps more. By that year also, for the first time in history, a single continent—namely Africa—will have a Christian population exceeding 1 billion.

The proportion of South Koreans who identify as Buddhist has been in freefall since the start of this century. Korea’s Christian pastors are scarcely more optimistic about their chances of holding on to the country’s youth. Besides Korea, the other Asian land of ultra-low fertility is Taiwan, which this past year became the first Asian country to legalize same-sex marriage.

Some of the most startling fertility drops have occurred in the Islamic world, in nations like Iran. As recently as 1982, Iran’s TFR was around 6.5 children per woman, but today it stands below 1.7—again below that of Denmark. And not surprisingly, institutional religion is in deep trouble. By some estimates, Iran’s rates of mosque attendance run at perhaps 1 percent or 2 percent of the population, and barely 3,000 of the country’s 57,000 mosques are fully operational. Fertility rates have also plunged in North Africa, in the Arab Maghrib, and in states like Tunisia and Morocco.

American Situation

Wherever we go in the world, that fertility/faith nexus seems secure, and that equation obviously raises intriguing questions for the United States. Until recently, the United States was a nightmare for social scientists, as an advanced society with high levels of gender equality that nevertheless retained high levels of fertility and was notoriously religious. At first sight, that seemed to make nonsense of many social theories about the social roots of religion. Over the past 15 years or so, that picture has utterly changed. As recently as 2008, the U.S. fertility rate was still around replacement, at almost 2.1, but that dizzying slide then began, at least partly as a consequence of the economic devastation caused by the crash of that year. The fertility rate is now 1.7, and almost certainly it will fall farther in the coming decade.

In the same years, another trend pointed to a drift away from organized faith, in the shape of the country’s rapidly ascending population of Nones. As I suggested earlier, we must be careful about not confusing these people with atheists. A “None” is a person who tells a pollster she or he has no religious affiliation. That may or may not mean anything about their degree of religious belief or practice: the none category tells us about belonging, not believing.

But those non-belongers are proliferating mightily. A common estimate suggests that America’s three largest constituencies today are Catholics, evangelical Protestants, and Nones, each holding around 23 percent of market share. In each successive survey, the proportion of Nones is significantly larger among young adults and millennials, presumably indicating that the proportion of Nones is destined to grow significantly in coming decades. One study in 2016 found that almost 40 percent of those aged 18–29 were religiously unaffiliated non-belongers, and even among those aged 30–49, the figure was 29 percent. The Nones, moreover, have grown in precisely the years of the demographic realignment, and the fall in fertility rates. That neatly fits the model of an emerging low-fertility and low-faith society. A European model, in fact.

Larger Context

Is this a fire alarm in the night for American religion, and more specifically for Christianity? Before despairing, we might consider some other aspects of the demographic picture. A low-fertility society is an aging community, one that needs plenty of young and hardworking people to do the jobs and pay the taxes, and that means foreign immigrants from poorer, high-fertility countries. Such immigrants bring their religions with them and lay new foundations in their host countries. We hear so much about the new Islamic presence that immigration has created in Europe, but far less about the reshaping of Christianity by migrants from Asia, Africa, and Latin America. Such Christian immigrants are already strengthening and transforming church life in Europe and North America, and even in the Arabian Peninsula. Christianity might be changing its ethnic character, but it has often undergone such transitions in the past.

Further, that global fertility shift is by no means uniform, and is far from having any serious effect on such vital regions as sub-Saharan Africa. Here, Christian churches are growing almost too fast to count, and these communities are abundant sources of migrants for areas such as Europe. By 2050, people of African origin could constitute a third of the world’s Christians, perhaps more. By that year also, for the first time in history, a single continent—namely Africa—will have a Christian population exceeding 1 billion.

Finally, my argument isn’t that Euro-American religion is dying, but that it’s changing. Many millions believe without belonging, and that number will grow. The challenge for churches, then—for all churches—is to decide how to respond to this new world, so hostile to institutions and hierarchies, so resentful of intrusions into what’s so widely seen as private space and private morality. How do you speak to those who wish to believe, but dread belonging?

How do you speak to those who wish to believe, but dread belonging?

And above all, churches have to think about those demographic trends, and why they are happening. Centrally, that means addressing the needs and concerns of women, whose shift from the home to the workplace and the college has been a driving force of this social tumult. What does this mean for presenting the Christian message?

The demographic revolution subverts or renders irrelevant so many features and activities that religions have long been viewed as essential to their existence and work. As those features fade, so religions of all kinds are forced to revisit and reconsider their core purpose. That exercise in rethinking and refocusing could be prolonged and even painful, even for religions that hold fast to historic beliefs. But the potential opportunities are rich indeed, and at a time of special human need. An empty planet needs far more than empty faith.

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