Explaining Falling Birth Rates

Norms on Mate Search

One possible explanation is changes in norms and legal rules that make mate search more difficult. An example is a norm against dating fellow employees and a stronger norm against dating someone who has authority over you or you have some authority over.

For many people, their job is the only context in which they routinely interact with lots of other people, the best environment for mate search. The interaction often provides a way of evaluating someone for characteristics such as honesty and competence as well as compatibility, much harder to do in the context of dating, harder still in computer dating. It works better for people who not only are fellow employees but are actually working together, which often means one just above the other in the office hierarchy.

The same issue arises in the university context. Undergraduates are free to date each other — mate search is arguably one of the main functions of college. Junior faculty members, likely to be unmarried, are commonly not supposed to date students, even students not taking classes from them, certainly not students who are. I am not sure what current norms are for graduate student/undergraduate interaction, expect graduate student/faculty romance to be at least somewhat frowned upon, especially if the faculty member has some authority over the student which is likely if they are in the same field, the context in which they are most likely to get know each other.

Another cause for declining birth rates might be changing norms of courtship. I have not been part of that market for over forty years but I gather from what younger people say online that many men believe that making advances that do not turn out to be wanted is not only embarrassing but dangerous, that they risk being accused of harassment or some related offense. In the student context, many men believe that if a romantic partner changes her mind she can get him into a great deal of trouble by taking advantage of a college disciplinary process heavily biased against men. I do not know to what degree that belief is true but many men believe it is, which could be expected to discourage courtship.

Along related lines:

Also, when I was working for a big time international consulting firm, they tried to come out with a formal rule that said that you were allowed to ask out a co-worker, but only one time.  If they said no, you could never ask again.  Apparently the Italians howled with laughter and insisted that if this rule was enforced in Italy, no one would ever have kids, as the typical Italian courtship approach involves like a dozen rejections before ultimately the woman finally gives in. (GoneAnon)

That cannot be the full explanation since Italian birth rates are down too. Since birth rates are down in all or almost all developed countries and many less developed ones, it is worth investigating how widespread the relevant norms are

Housewife Becoming a Low Status Profession

For a very long time, the default system for producing and rearing children was a married couple, with the husband producing income and the wife in charge of running the household and rearing the children. Over recent decades, the woman’s role in that division of labor has become a low status activity, lower status than making a living in the marketplace, much lower than professional success.¹ Being an unmarried adult woman used to be, in most contexts, low status, on the presumption that if she could have caught a man she would have. At present, in much of western society, that has reversed — being a married housewife is lower status than being an employed single woman.

…arguments from the stay-at-home moms I know, who say people are constantly giving them grief about it, and who are often looking for some part-time make-work job they can take just so people will stop giving them grief about being a stay-at-home mother (Scott Alexander)

It is possible for a married woman to have both a job and children or for an unmarried woman to have children, but the former is more difficult than for a full time housewife, the latter much more difficult.

The Same-Sex Alternative

Another possible explanation for declining birth rates is the increasing acceptability of same sex relations. An mm or ff couple can produce a child by one of them, more easily for ff, but that is a less attractive option than for a bisexual couple, adoption more likely.

Why Expect Replacement?

Fertility rates below replacement are widely viewed as an anomaly, something surprising, probably because almost all past societies, including ours, had stable or growing populations. The explanation of that pattern was provided by Malthus more than two hundred years ago: People like sex, sex produces people. If incomes for the bulk of the population are  high enough so that couples can afford to produce and rear children they do so. Population expands, pushing against a limited supply of land on which to grow food, which pushes incomes down. Either mortality goes up, marriage ages go up, or something else reduces fertility. The result is that population is usually at the level at which the mass of the population can afford to produce and rear enough children to keep it at that level, going up a little if something, such as improved agricultural technology, raises the equilibrium level.² That is, to a first approximation, the story of the past many thousands of years.

But not of the present, since we now have both reliable birth control and societies far above starvation — real per capita income in the developed world is about twenty to thirty times what the global average was through much of history. That eliminates both the force pushing population up and the force keeping it down. We could end up with a fertility level higher or lower than replacement. Malthus, writing in the early 19^th century, came up with a brilliantly simple explanation for the behavior of population just about when it ceased to be true, first with population growth in the 19^th and 20^th centuries and then with population decline in the 21’st.

There is still a mechanism to push fertility back up — eventually. Some cultures, such as the Amish or the Haredi, have high birth rates and it is likely that some people have an innate tendency, heritable, to want children. If nothing else about the society changes, over time one would expect philoprogenitive people and cultures — to the extent that such cultures succeed in reproducing themselves — to outbreed other people and cultures, pushing birth rates back up.

How long would it take? The Amish population doubling time is about twenty years and there are currently about a third of a million of them in the US. If that growth rate continues, in a century there will be about ten million. There are about 700,000 Haredi in the US. Their global growth rate is 4%, a little higher than the Amish. I could not find a figure for the US Haredi but since most of the rest are in Israel and are said to have a higher growth rate than the US Haredi it is probably a little lower. So figure than in a century there will be about twenty million. Assuming that there are a few other groups I am not counting and that the US population declines somewhat over the next century, that suggests that in a century something close to twenty percent of the population will be descended from philoprogenitive groups. I have no estimate of how many will be descended from philoprogenitive individuals, but in about a century the effect of that mechanism, genetic and cultural selection for high fertility, could become significant.

Given how rapidly other relevant features of our society, technological and cultural, are changing, “nothing else  about the society changes” does not seem likely.

P.S. A friend suggested Mormons as another philoprogenitive group. There are about seven million in the US. The growth rate of the religion is about .9% a year, the birth rate only about .5%, which presumably means that some of the growth is conversion. The former rate, if continued, implies about 17 million in a century, the latter about 12 million.

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1. For a much more detailed presentation of this explanation, along with arguments against a variety of alternatives, see It's embarrassing to be a stay-at-home mom.

2. Ricardo offered a more sophisticated version of the model in which the equilibrium depended on the tastes of the working class, in his world the bulk of the population. The more luxurious their tastes  the higher their incomes had to be to make them willing to bear the costs of producing children, a tradeoff between the pleasures of sex and the pleasures of consumption and leisure, and concluded: “The friends of humanity cannot but wish that in all countries the labouring classes should have a taste for comforts and enjoyments.”