Note: I didn't write this essay, nor do I own the blog where it came from. I'm just sharing it. The essay text is displayed below this line.

I recently put out a post on fertility collapse, The Paradox of Low Fertility, in which I claimed that the fertility collapse is mostly due to modern birth control. Some people disagreed with this explanation. One person, Peter Rabbit, said:

Your theses regarding the pill is a bit outdated. I would recommend arcotherium’s piece overviewing the four phases of demographic transition (in the West). A quick rebuttal is to point to France’s history.

I responded:

Yeah, I’ve read it. He underestimates the importance of birth control. I don’t think I mentioned the pill in the essay. Birth control is a more general notion, which includes many things, including the pill, condoms, abortion, the rhythm method, etc. E.g. in Japan, after WW2, they relied heavily on abortion to limit fertility. The point I’m making is that people have an increased ability to limit reproduction. Women also have an increased ability to delay marriage. There are multiple factors involved (which I described) but birth control is very important. There was a big collapse in fertility after the birth control pill was introduced in the West.

I am going to expand on what I said there, and respond to some of the points in Arctotherium’s essay, which mostly ignores birth control as a cause of low fertility.

His essay begins with the paragraph:

Human net fertility is complicated. Some things that matter on the margin: winning elections, baby simulators in health class, war, housing costs, religion (both type and intensity), women’s education, population density, racial diversity, STD-induced infertility, baby bonuses, antinatal propaganda campaigns and sterilizations, and status-messaging in soap operas. The full list is much longer. But most of these factors are just not that important—a few percent here, a few percent there, and with sharply diminishing returns.

Birth control is conspicuously absent, as if the birth control pill, latex condoms, IUDs and safe abortions had no effect on fertility whatsoever. You could argue that birth control is not the primary cause of low fertility, but to completely ignore it seems a bit strange.

Some people might say “Birth control has existed for a long time, and thus it couldn’t be the cause of this recent change”.

Of course, birth control is not entirely new. Some methods of birth control have existed for a very long time. Abstinence is the simplest, but it requires overriding sexual impulses. The rhythm method (periodic abstinence during times of ovulation) is a bit more sophisticated. It requires some education, and is made more effective by having an accurate thermometer. Withdrawal is another old method, but it requires overriding the sexual impulse near the moment of orgasm, and it doesn’t always work. Condoms made from animal intestines were used in the past. There were also primitive, dangerous methods of abortion.

Modern birth control methods are much more effective, because they are convenient, reliable and safe. The latex condom and the birth control pill are very effective at preventing pregnancy, don’t reduce the pleasure of sex very much, and require little impulse control. So, they are much more effective than old methods. Modern abortion is also much safer, and is readily available in most Western societies.

Modern birth control gives the individual much greater control over reproduction. It is an expansion of human agency. It makes reproduction into a choice, rather than a likely consequence of having sex. I believe that the modern fertility collapse is primarily due to this expansion of agency.

Before getting into the evidence and arguments, it’s worth taking a moment to consider the moral/political reasons why some people might prefer the cultural-values explanation over the birth-control explanation.

The cultural-values explanation is popular with conservatives and reactionaries, because it allows them to blame the left for the fertility collapse. And it’s true that the left has been waging cultural warfare against family values for decades: promoting sexual liberation, encouraging women to become financially independent, denigrating motherhood and the nuclear family, cock-blocking men, and so on.

There is also a deep aversion to biological and psychological realism about human nature. Most people have an essentially magical view of human nature. They don’t think about human beings as machines that can malfunction.

Now, let’s dive into the evidence and arguments. I’ll start with a chart that Arctotherium used in his essay, showing the TFR over time of the Netherlands, combined with the infant survival rate. Unfortunately, I don’t know the source of this chart, but it seems right to me, so I will assume that it is correct. It should be representative of the general changes in Western fertility.

This chart shows the “demographic transition” very clearly. During the 1800s, fertility was roughly 5 children per woman, but only about 3.5 of those children survived infancy on average. Although women are capable of having 10 or more children, 5 is a rough estimate of the natural fertility rate for a women who survives to menopause.

For most of human history, most people died young, during infancy, childhood or adolescence. The current low rate of premature death is a historical anomaly, made possible by recent advances. This condition is not stable. In a balanced state, excess reproduction is balanced by a high premature death rate. We are living in a strange time, and we should keep that in mind.

As more children survived past infancy, the fertility rate declined, probably due to two factors: prolonged nursing and economic considerations. To some extent, existing children displace potential children. Some methods of birth control were available in the 1800s. There was also an increase in education, women working outside the home, urbanization, etc. However, the average number of children surviving infancy remained at roughly 3. During this time, the population grew, due to the advances of modern civilization (hygiene, medicine, more food, etc.), which allowed a greater percentage of people to survive from birth to adulthood.

Fertility dipped during WWI, for obvious reasons, and then rebounded, before falling again during the 1920s. What caused the dip in the 1920s? One likely explanation is the latex condom, which became widely available after its invention in 1920. Arctotherium does not explain the rapid decline after 1920. He seems to view it as part of the longer trend of declining fertility, due to family planning (in other words, birth control).

(see the rest of the post in the link)