The Great Replacement Theory (GRT) is not new to this country.1 Recently, it has helped motivate the current Administration to attempt mass deportations. This policy is counterproductive on many fronts. Reducing diversity weakens our culture, contrary to the claims of the GRT advocates. In addition, it may exacerbate a trend toward a declining population, which those same advocates find alarming.

As a youngster, I was an avid reader of science fiction. The 1953 novel Childhood’s End, by Arthur C. Clarke, is truly a classic. I was reminded of my fondness for it by a recent article in The New Yorker entitled The End of Children. If the topic of this post interests you, I suggest you read the entire article.

In 1968, Paul Ehrlich, a lepidopterist, and his largely uncredited wife, Anne, published a best-seller called “The Population Bomb.” For centuries, economists had worried that the world’s food supply could not possibly be expected to keep pace with the growing mobs of people.

In my recent Berkshire OLLI course, I promoted the notion that economic policy focused on GDP growth is misguided. “Gross Domestic Product” is a measure of the value of all final goods and services produced in a country. The word “final” refers to the idea that only items purchased by a consumer will be counted, not intermediate sales (for example, tires sold to an automobile manufacturer will be resold when the car is assembled, as part of the total price). Only the value of the completed product will be counted, not all of the intermediate steps.

One problem with using GDP as a measure of economic activity is that the focus becomes one of “more is better” when, in fact, GDP is not a measure of satisfaction, or any other metric that reflects the quality of life. Another problem is that “consumption” is simply the flip side of “destruction” — for every “good” we consume, a resource is destroyed.

A cotton shirt, for example, is made by destroying several plants that absorbed resources from the soil. The wool for a sweater does not destroy the sheep it comes from, but that sheep had to eat for a year in order to produce the wool. A polyester garment is made by destroying a non-renewable resource. And all of these will ultimately end up in a landfill where they will sit for thousands of years.

Paul Krugman opined (a month ago) that

… there has been a surge in imports as companies race to get stuff into America ahead of Trump’s tariffs, or possible tariffs, or whatever is going on in his mind. But these were for the most part durable items that could be and have been stored. So as I understand it, the import surge should be roughly matched by a surge in inventories. And this in turn means that there won’t be much effect on GDP: higher imports reduce measured GDP, but inventory accumulation increases it, so the overall effect should be more or less a wash.

Since, then, Krugman’s tune has changed, and it now appears that GDP in the US is headed for “negative growth” — a euphemism for a recession.

Another factor pointing toward a long-term decline in GDP is the likely loss of population in this country. And we are not alone. Almost every industrialized country is experiencing a declining birthrate. Japan is of interest because it has for many years been disinterested in welcoming immigration. This is a pattern than may appear in the United States if we are successful in reducing immigration, even in if the mass deportation schemes never work as advertised.

The headline word “Irreversiable” may be overly dramatic. See my discussion below of the logistic map as to why there may be a downside limit.

Meanwhile, The New Yorker article cited earlier has supplied some sobering statistics. Sobering, that is, if you are worried about the future of Social Security and other retirement programs that depend on more younger workers to be paying into the program. Less sobering, perhaps, if you are more worried about climate change and the per capita (mis)use of resources.

The article properly defines the “total fertility rate” as the number of children the average woman would have during her lifetime.2 The “replacement rate” is given at 2.1, which means that all women in the population average that number of births, then the population size will remain constant. Any number above that means the population will grow, and a lower number points to a declining population.

Japan has a total fertility rate (TFR) of 1.3, which results in the pattern seen in the chart. The United States is now at 1.64, so absent immigration, our chart will show a similar, if less dramatic, decline in the years ahead. In South Korea, the number in 0.73, which some have suggested means that the country will lose all its population within 3 or 4 generations. I suspect that will not happen.

Most of the countries with high TFRs are in Africa. Other industrialized countries show low rates:

• Canada 1.37

• Like Japan; Singapore, Spain, and Italy all have 1.3

• Australia is the same as the US, 1.64

There may be a limit

I’ve played a lot of bridge, but I never had this experience:

My first encounter with … complexity [science] came while I was playing bridge in the early 1970s. My partner was Robert (now Lord) May, and I couldn’t understand the squiggles and marks he was making in a notebook on the corner of the table when he was not playing a hand. I had no idea at the time that he was making history.

from The Perfect Storm: The Science of Complexity in Everyday Life (2009) by Len Fisher, pp. 13-14

Lord Robert May introduced the logistic map in 1974.

I expanded on this concept in my work on Wall Street, developing learning models for predicting such things as currency exchange rates. Today, those efforts would be labeled “AI” and be worth a billion dollars, but in those days it just seemed like fun.

May was observing how populations would expand and then crash, and he was looking for a way to model that phenomenon. We see it all the time in the natural world. In a mast year, oak trees produce so many acorns that the squirrel population cannot eat them all (assuring the start of future oak trees). The next year, there are many more squirrels around, but the oak trees produce very few acorns, so the squirrel population declines. This up and down pattern can be seen in other pairs, such as foxes and rabbits.

The takeaway from all of this is that, in the long run, nature finds a way to maintain a balance. The ups and downs may appear random, but they actually follow a (more or less) predictable pattern. Humans, however, may have outflanked nature by inventing ways of introducing new resources (such as nitrogen fertilizers and new varieties of rice). Still, there may be limits that even human ingenuity cannot overcome. And these limits may be psychological as much as physical.

If, as seems to be the case, enough people decide, for whatever reason, that having a(nother) child is not desirable, then the logistic map may give us some insight into the future. One such insight is that a population crash does not mean the end of the species — it is just a breather to let available resources catch up with the population requirements. We can hope. I don’t expect to be around to see the end of this movie.