A Trend Toward Decreasing Fertility

               Adhering to the Biblical admonition in the first chapter of the book of “Genesis” to “be fruitful and multiply” takes some doing.  Even if infant mortality is low, women must give birth on average to 2.1 children for a population simply to achieve replacement level (at least for a population in which life spans are not increasing and immigration is not significant).  For a population to multiply, even just to double, within one or two generations requires devoting a great deal of time to birthing and caring for children. 

               As Michael Teitelbaum and Jay Winter underscore in a recent article in the New York Times, fertility rates have been generally decreasing since the post-World War II baby boom.  Currently, the United States is at replacement level, while many European nations and Japan have been below replacement level for more than a decade.  The authors observe that such low fertility levels are not confined to the developed world, noting that fertility has fallen below replacement level “in places as diverse as Armenia, Bhutan, El Salvador, Poland, and Qatar.” 

Beneficial or Calamitous?

               Decreasing fertility is typically framed negatively in terms of a dearth of new workers available to support the needs of an expanding group of retirees, who are living longer and longer. Commentators have spilled considerable ink over the past dozen years or so anticipating momentous generational conflicts resulting from such trends.  Teitelbaum and Winter argue, however, that low fertility rates are often a good thing for societies, since they seem to be connected with greater opportunities for women, higher levels of productivity, political stability, and less migration driven by economic desperation.

               Diminished fertility, however, can be every bit as worrisome as fertility rates that are high enough to produce the multiplication that “Genesis” enjoins.  (With but a few exceptions, such high fertility is concentrated in the nations of sub-Saharan Africa.)  Just as populations can increase geometrically, so too they can decline precipitously.  In his book, Big Gods, Ara Norenzayan recounts a hypothetical study from the website of the Economist that shows that if current fertility rates in Hong Kong were to persist and were the sole relevant factor, that city of 3.75 million females would collapse to a single daughter in only 25 generations -- what Teitelbaum and Winter term a population “death spiral.”  According to the United Nations, 83 nations could face a similar fate eventually, given their current fertility rates. 

Shake or Bake

                Norenzayan is interested in fertility rates for a different reason.  He highlights how elevated fertility rates constitute a substantial reproductive advantage for many religions in the competition among groups.  Proselytizing religions can grow by acquiring converts, but religions can thrive and increase membership even more readily on the basis of their followers’ prolific reproduction and investment in their children.  The Shakers, a nearly extinct religious group, which forbids members to procreate, are probably the most famous of the strikingly unsuccessful exceptions to this pattern. 

               In multiple studies that have been done on the topic, religious people and members of tightly knit religious groups, especially those with Norenzayan’s Big Gods, reproduce at far higher rates than non-religious people and atheists.  In such studies the latter groups usually reproduce at rates well below the 2.1 average of births per woman replacement rate, even in societies that pursue various policies supporting higher fertility rates, including such things as financial bonuses, tax incentives, mandatory paid parental leaves, and enhanced availability of inexpensive child-care.  The rise of secular societies and the efforts of the New Atheists notwithstanding, one good reason to bet on the persistence of religion, in general, and of some religions, in particular, is that so many encourage and support adherents in their efforts to be fruitful and multiply. 

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