Are There Internal Limits to Growth?
I am still very hard at work on my Scaling in Human Societies project. Today’s post is part of that project, but for now I will turn away from urban design and toward sustainability.
The Limits to Growth
“The Limits to Growth” is the title of an infamous 1972 report from the Club of Rome, by Donalla and Dennis Meadows, Jørgen Randers, and William Behrens III. That report is based on the Club of Rome’s World3 computer model, which incorporates five variables: population, food production, industrialization, pollution, and nonrenewable resource consumption.
Most people who are familiar with the report know that it has not aged well. Starting on p. 56, for instance, is a chart of various nonrenewable resources and projections of how long they will last. Considering static projections (the reserve/production ratio, based on what reserves and production were at the time), copper, gold, lead, mercury, natural gas, petroleum, silver, tungsten, and zinc should have run out by now. But these projections were based on static consumption from 1972. If instead we take into account an exponentially growing annual usage, then aluminum, manganese, molybdenum, and platinum group metals should also have run out by now, and nickel will run out in 2025. The authors think they are being generous by also forecasting depletion with five times known reserves and exponentially increasing consumption. Under those assumptions, petroleum and natural gas, among other resources, should have run out by now.
The report discusses technological development in dismissive terms in Chapter 4. If technology can extend the life of resources, then human prosperity will be curbed by runaway pollution. And if better technology for pollution control can be developed, then human prosperity will be curbed by limits in food production. The report projects that under the most optimistic technology scenarios, an end to growth should be expected by 2100.
The Limits to Growth shows an interesting juxtaposition between extreme pessimism about human civilization’s ecological outlook and faith in the capacity of technocratic control over the trends shaping that outlook. The core of the problem, clear in Limits and in many other works from the environmental community at that time, is human population. Limits played no small role in inspiring the late 20th century’s horrific population control policies.
Shortly after the report’s release, Allen Kneese and Ronald Riker of Resources for the Future testified to the U.S. Congress on the problems with the modeling on “technology” in Limits. The report was structured in a way that treats population and resource use as growing exponentially unless stopped, but with a limited or no role for technology. According to the testimony, this was a deliberate modeling decision to make the results, including the “optimistic” case, look worse, and not merely an innocent limitation on the knowledge that was available at the time. Computer modeling for ecological forecasting was still novel as of 1972, giving the enterprise an air of authoritativeness. But the old maxim in computer science, going back to Charles Babbage, is “garbage in, garbage out”. No model, however sophisticated, is better than its input data, and if the World3 model uses faulty assumptions, then the output will inevitably be faulty.
There Are Limits, Right?
I have made no attempt to disguise my disdain for Malthusian forecasts such as in Limits. Julian Simon, in The Ultimate Resource, offers a much better treatment of the subject. Simon portrays a much more robust role for technology, which has arisen to deal with past resource and pollution pressures, and treats natural resources as effectively infinite. The “ultimate resource” in the book’s title is human population, as it is people who innovate and come up with technological solutions. It is the polar opposite of ecologic reasoning that human population is a problem that needs to be curbed. Forty years after The Ultimate Resource was published, much improved pollution management and false resource scares such as peak oil have largely vindicated Simon’s work.
Still, an attentive reader will notice the word “effectively” in the preceding paragraph, because we all know that natural resources are not literally infinite. We might start from first principles in establishing limits. Under established laws of physics, civilization’s potential is capped by the speed of light, the Heisenberg Uncertainty Principle, and the laws of thermodynamics, which respectively limit the ability to project human civilization out into space, into a small size, and into the future. The fact that there remain mysteries in fundamental physics offers only the slightest hope for evading these limits, but one can take comfort in knowing that they are far beyond what modern civilization has achieved. Bostrom (2003), for instance, wrote on the ethics of delaying technological development,
As a rough approximation, let us say the Virgo Supercluster contains 1013 stars. One estimate of the computing power extractable from a star and with an associated planet-sized computational structure, using advanced molecular nanotechnology2, is 1042 operations per second.3 A typical estimate of the human brain’s processing power is roughly 1017 operations per second or less.4 Not much more seems to be needed to simulate the relevant parts of the environment in sufficient detail to enable the simulated minds to have experiences indistinguishable from typical current human experiences.5 Given these estimates, it follows that the potential for approximately 1038 human lives is lost every century that colonization of our local supercluster is delayed; or equivalently, about 1029 potential human lives per second.
Even these extreme numbers, though, imply limits to growth that are comprehensible over meaningful time scales. Approximating to an order of magnitude, world population is now about 1010, leaving a potential growth of a factor of 1028 to achieve full colonization of the Virgo Supercluster. If the trend of falling birth rates is reversed and civilization attains a stable rate of population increase of 1% per year (here, “population” might refer to biological humans or brain emulations), Bostrom’s numbers will be achieved in about 6500 years. That length of time ago would put us in the Neolithic, after the advent of agriculture and settled communities and before the advent of writing. As long as we assume plausible physical limits and reasonable growth rates (see also Brian Wang’s somewhat whimsical take on the subject), the conclusions will be similar.
I present this as a thought experiment, not as a projection that there actually will be maximal computronium brain emulations in the Virgo Supercluster, but as an illustration that there are at least theoretical limits to growth under established physics. We can then ask what those limits are and whether they are tighter than the theoretical limits established by physics.
Internal Limits to Growth
Now I want to turn to Manfroni et al. (2021), whose paper is entitled “The profile of time allocation in the metabolic pattern of society: An internal biophysical limit to economic growth”.
Manfroni et al. consider the word “Malthusian” and its evolving use over time. The term goes back to Thomas Malthus’ (Malthus (1798)) An Essay on the Principle of Population. In that essay, Malthus argued that human population should increase geometrically (that is, by a fixed percentage every year) while food production should increase arithmetically (by a fixed amount every year). In this case, simple mathematics dictate that the amount of food available per person should decrease over time, to what Malthus assess to be a subsistence level.
Over time, “Malthusian” has evolved to refer to any situation in which resource availability is not able to grow to meet societal demand. Manfroni et al. notes that the term has further evolved to refer to a situation in which pollution sinks, e.g. the planet’s capacity to absorb greenhouse gases, are unable to match demand, thus again pushing society to a subsistence level via pollution.
Both of these uses of the term frame sustainability challenges as a black box model. Society is constrained by two main external factors of resource availability and pollution. Manfroni et al.’s use of “internal” attempts to open the black box and consider internal limits to growth. This would be a novel use of the term “Malthusian”. Sometimes broadening the definition of a term is a helpful way to find that term’s essential meaning. Sometimes broadening the definition of a term introduces confusion and ambiguity.
The particular limit that Manfroni et al. are concerned with is working hours. Although not including in the paper, this plot from Our World in Data is important context.
Manfroni et al. cite Zipf (1941), who argues in the wake of the Great Depression that further economic progress must rest on consumption. This is an important point that goes beyond what is in Manfroni et al. and one that I hope to discuss more thoroughly at a later time. The idea that modern economies are driven by consumption, and that increasing consumption is necessary to drive economic growth, is one that persists in the popular imagination. But the field has long since moved on.
If we accept that consumption is the driver of economic growth, though, then we have a paradox. Consumption requires more leisure time, as shown for example by the working hours plot above. But labor is itself foundational to economic growth. It is inherent in the widely-used Solow-Swan model (and many variants thereof) of growth; see Solow (1956) and Swan (1956) for the foundational papers. Consequently, economic growth must eventually be self-cannibalizing: more growth → more leisure time → fewer working hours → growth constrained.
Manfroni et al. discuss three issues related to their model. Comparing China to the European Union, they assess that China has more room to grow. They have—at least officially—a lower dependency ratio, which is the ratio between working population and people who can’t work (e.g. children, the elderly), and also a larger share of their workforce in manufacturing.
Second, they consider the impact of trade. Considering working hours embodied in products, Manfroni et al. find that the EU imports 566 hours per capita per year and exports 101 hours per capita per year. By comparison, China imports 88 hours/p.c./yr and exports 156 hours/p.c./yr. They don’t assess these figures for the United States, but I would imagine that the U.S. trade balance sheet is similar to that of the EU. All this should call into question the feasibility of replacing a large amount of imports with domestic labor, as either that labor would have to come from some other type of job, or it would have to cut into leisure time or time spent for other purposes.
Third, they consider the impact of immigration. In Spain, where the authors place particular focus, immigrants tend to be younger and without children (at least when they migrate), thus providing Spain with more working hours.
Manfroni et al. discuss Bouvier (2001), an analysis of a report from the UN Population Division that proposed immigration as a solution to subreplacement fertility in wealthy countries. Whatever one thinks about immigration policy, and I am very much in favor of nearly open immigration myself, this is clearly not a long-term solution. For one thing, the politics around the issue are toxic, and there is no sign of improvement in sight. For another thing, since immigrants generally move from poorer to wealthier countries, the immigration pump of the UNPD requires that a wealth differential between poor and rich countries persists indefinitely. For a third thing, the impact of emigration on countries (e.g. the risk of brain drain) is not well-understood, but the same analysis of Manfroni et al. suggests that their own development may be impeded. And for a fourth thing, falling birth rates have been observed over the whole world, and many countries that are still considered to be relatively poor are themselves as the subreplacement level, suggesting that even if the politics of high levels of immigration are feasible, the possibility may be diminishing.
The question of fertility is not directly discussed in Manfroni et al., but it is impossible not to think about. This is an issue that, for as much as I talk about it, I don’t feel that I understand very well. But it seems plausible that the same forces that would lead people to choose to work fewer hours would also lead people to choose to have fewer children or none at all.
Are There Internal Limits to Growth?
Last week, I stated,
My biggest concern, though, is whether the prosperity that urban success generates also produces lifestyles and political ideologies that are ultimately not conducive to future success. Questions of sustainability are very much a part of discussion around urban design, and I share those concerns, even if I have a somewhat different take on the subject. But this is another topic for another day.
A way in which those lifestyles and political ideologies manifest themselves is with fewer working hours. Many people in the progress studies movement, for instance, like to celebrate the above plot of working hours. But a decrease in working hours in an effect, not a cause, of economic progress.
As with the 1972 Limits report, Manfroni et al. suffer from the weakness that they do not seriously treat the potential of technology to address the contradiction posed by internal limits. It is not at all clear at this point how much potential recent advances in artificial intelligence may have to substitute for human labor, or how many more advances may arise in the near future. With population aging, the demand for labor saving will only grow, however.
Quick Hits
On the Scaling in Human Societies project, a post on urban scaling is now available. The content is similar to last week’s post on the subject, but I elaborated on a few points, particularly the question of assessing causality. This issue now haunts me: we know that larger cities tend to be more prosperous, but to what extent does size cause prosperity? And sure enough, when I dug into the matter a bit, I found it to be much less straightforward than I had expected.
The last Sears in Washington state has closed, bringing the once iconic retail chain down to eight locations in the United States. A few years ago, Company Man did an episode on why Sears has gone into terminal decline. Sears was once headquartered in the tallest building in the world, and in 1991, the New York Times reported that Walmart had surpassed Sears as the top retailer in the United States. The older generation may be saddened, but for people my age and younger, Sears has always been yesterday’s news and will not be missed.
A few months ago, a paper found great risk to public health from cooking utensils made of black plastic. Carcinogenic flame retardants are not used in black plastic manufacture directly, but some flame retardants find their way in from recycled feedstock. However, the paper has gotten back in the press this week due to an embarrassing math error. Here is the offending line. For those who are not familiar with the issue, I will leave it as an exercise to find the mistake.
This compares to a ∑BDE intake in the U.S. of about 250 ng/day from home dust ingestion and about 50 ng/day from food (Besis and Samara, 2012) and would approach the U.S. BDE-209 reference dose of 7000 ng/kg bw/day (42,000 ng/day for a 60 kg adult) (United States Environmental Protection Agency, 2008).