Synopsis: Optimum depends on criteria.
There is an upper limit to the possible human population, constrained by the total biomass the planet supports, and even more constrained if we wish to share the planet with other species and exist sustainably. Clearly, population growth cannot continue indefinitely. Population growth must end eventually, but what is the target ideal population?
This is a look at the arguments for alternative possible population targets.
Using the analogy of the egg farm, you can operate the farm for the largest population possible, but if you have to live in the farm as the chickens do, then there is an optimum population where you are neither lonely, nor overcrowded.
Like the farmer vs the chickens, not everyone has the same perspective on what population is optimum. However, even for us in the role of “chickens” there can be different philosophies, such as some believing a lower living standard for the chickens would be acceptable, if it allows more chickens to be alive at one time. The principle of Jeremy Bentham suggests it may be worth having double the population if those people can be more than half as happy. On the other hand, suicides are evidence that happiness can also be negative, so only a small decrease in overall happiness can swing the value from positive to negative, or at least make a huge change in net happiness.
While the most people needing to share the less per person, the wealthiest get an increasing share and increasing wealth as population increases, creating another difference in perspective.
The goal here is to examine the arguments for larger population and those for smaller population.
While I do believe there is a range of population levels that could be described as ‘optimum’, at this stage I am not yet suggesting either no upper or lower limit. Whilst I feel that a population of 1 billion will likely fall within the optimum upper and lower boundaries, that is just a guess that will not create any confirmation bias as I continue to research the topic.
Where I do take a perhaps radical step, is that the goals align with the stated goals sustainability++ of this site:
- Sustainability: There needs to be a path to sustainability beyond primary dependence on one finite planet.
- Plus: Here for a good time is the goal of maximising the experience of each individual.
- Plus: Here for a longer time means perusing the goal of being able to extend life beyond the limitations of one finite planet.
This is a topic that has previously been given a significant amount thought, at times by some very significant thinkers, who often have very different goals.
Many studies are by economists, and consider maximum economic output.
The biosphere: a limit to the possible human population.
While the recent population explosion was unprecedented, there has been human population growth throughout history. Yes, it was more gradual previously, there have been minor setbacks, but all of human history makes population growth appear normal.
Yet this pattern of continuing growth over such a long time is unique to humans. The Earths total biosphere is declining from its peak 500 million years ago, so overall, humanity is running against the trend. Without the total biosphere increasing, the percentage of all life that is human is gradually increasing. Could it one day it become just us, our food and our pets? Logically, population growth must stop at some point.
Given the reality that population growth must stop at some point, the next question becomes at what number will, or should, population growth stop.
Should humans try for the maximum population possible within our finite space, like chickens in a maximum production egg farm, or should we go ‘free range’ with a lower population in order for each individual to be able to have a better life?
Environmental/Ecological Footprint: Sustainability can be the easy part.
For each person, their lifestyle determines an ‘ecological footprint’. This is about the number of people who can sustainably exist in a given area of an environment. Exceed that number, and the environment will be damaged and eventually collapse from being over carrying capacity. The area of the environment, divided by the people it can carry, provides a per person footprint, or amount of space required per person. An interesting calculation is to take the environmental footprint per person of a given lifestyle, multiply this by the number of people in the world, and then you have total space required for everyone in the world to live that lifestyle. Several web sites have already done this, and in this section two are considered.
On the data from the ‘per square mile’ site, if everyone lived as those in each of the following countries, the required percentage of the Earth’s land would be:
- Bangladesh: 33%
- India: 50%, Uganda: 75%
- China: 110%
- Costa Rica: 140%, Nepal: 190%
- France: 240%
- USA: 410%
- UAE: 540%
While I have not verified the data, although perhaps not exact anymore, the data was reliably sources, and will still be close enough for these purposes.
- is vegan and only eats locally grown unprocessed food.
- lives in a freestanding home without running water made of straw and bamboo.
- that is tiny and shared with 10 people, very efficient and without electricity (and it is all renewable?)
- does not travel by car at all, but it if they did it would be electric and they would carpool.
- never needed public transport or flights.
This reveals that if everyone lived following all of those above principles, then the world would need only 0.2 Earths, one which basis 40 billion being able to live on Earth.
Other equations are, but simply moving to:
- adding electricity and sharing the tiny home with only 4 people, only 80% of food being local, plus traveling 11 km per week by electric car and 3km by public transport, brought the quota to 0.4 Earths: 20 billion people supported.
- occasional meat, 30% local produce, multi-story concrete small highly energy efficient apartment with 2 people, 50% of power from renewables, similar trash to neighbours, 200kms per week in an EV 60% of time ‘carpooling’ and 34 kms of public transport and 1hr of flights per year, and 2.3 Earths are needed: 3.5 billion supported.
Notably, this requires zero people who live the lifestyle of the world’s richest 1%, who currently result in more than double the emissions of the worlds least affluent 50%.
This data for the world’s top 1% can be used as the basis for one more projection. How different would the data for Bangladesh be from the entire lowest income 50%? Even assuming that lowest 50% of the entire world averages half the per capita emissions of the nation of Bangladesh, that would mean 6x the footprint would be sustainable. However, the top 1% is creates double those emissions, which means 1% of people equate to producing 1/3 of the total emissions of a fully sustainable population of this planet. The required planets to support the entire population living this way?
- The World’s richest 1%: 3,300%, or 33 entire planets and six times more planets than required for the population to live like the average for the UAE.
Sustainable living alone does not support even 1 billion people without technology.
Consider paleolithic humans, who live on Earth for almost 300,000 years, and did so within all constraint of living sustainably. However, in all that time, their population never reached even 4 million, because as hunter gatherers, they could never achieve high population density.
This creates a catch 22: It takes technology to support high population density, but so far, societies producing technology have increased ecological footprints.
Current sustainability requires inequality.
To increase the number of people able to live sustainably as things are, what is needed, is a way to have a large number of people living sustainably, accessing technology produced by people living with the higher footprint that goes with a population that produces technology.
This would mean something like a USA, or even just California, developing all the technology that is in the rest of the world, for use globally by a population mostly existing like people today in Bangladesh with a very small environmental footprint.
What becomes clear is that, as things are, maximum population existing sustainably depends on inequality.
Global population options for sustainability.
Simplistically, taking 100% and dividing that by any of percentage numbers from the “per square mile” data above gives the multiple of the current world population that could be supported sustainably.
For example, 100% divided by 33% for Bangladesh gives a 3x multiplier, and 100% divided by the 410% for USA gives a 0.24x multiplier, and for the richest 1% it would be a 0.03x multiplier.
Applying those multipliers to the current 8 billion population produces 24 billion, 1.92 billion, and 240 million respectively. That does not mean it is possible for the whole world to like any of these examples, with a reality check still to be considered.
Maximum population reality check: Could almost all live like Bangladeshis?
Simply applying the footprint suggests that if the entire world lived like the people of Bangladesh, then a population of 24 billion could be supported sustainably, but is this really possible, or desirable and if so, for who’s benefit? Issues to be considered include:
- Does Bangladesh rely on offshore emissions?
- Year after year, Bangladesh imports more than it exports, and significant emissions result from the production of those imports in the country of origin.
- Would this reduce levels of medical, agricultural and other technologies?
- Even a small drop in technology could affect population despite a drop in footprint as demonstrated by the reality that even after 300,000 years there were only 4 million Paleolithic humans globally.
- Desirability: The change could enable continued economic growth through population growth?
- But it requires a fall in living standards for the vast majority of the population, so who gets the economic benefits?
Between the offshore emissions that do not count in the footprint calculator numbers, and a potential fall in access to technology, the sustainable population could be well below that theoretical 24 billion, but if everyone adopted this living standard and there was no more top 1%, it would certainly allow for further population growth.
The contradiction is that the motivation for further population growth is to allow the economy to keep growing, and if the economy keeps growing, who will own all the wealth? The only answer that would allow almost all the population to live like people in Bangladesh, is for the wealthiest 1% to still exits and be the reserve for that wealth, making them even richer than today. Of course, this wealthiest 1% already consumes around 1/3 of the world’s available total footprint, so the potential population falls to 10 to 12 billion.
In fact, this picture of falling wealth for the majority of the population with a small ultra wealthy group absorbing the proceeds of economic growth is exactly the pattern being seen in many western democracies in the 2020s.
Conclusion: A very real prospect with for a 10-12 billion population.
USA reality check: Could everyone enjoy a life like living in the USA?
This option requires the global population to fall to less than 2 billion, which would either take over a hundred years of population contraction or some type of disaster that makes the world less livable. Either of these scenarios rewrites all the rules for what is required for sustainable living in the new changed world, which makes this option purely hypothetical.
If it did somehow magically happen and the world was just like it is now with almost 2 billion people living like those inthe USA, would it be sustainable?
I think it would be close to sustainable. The USA today outsources manufacturing emissions to China, and bringing those manufacturing emissions within the economy would raise emissions per capita making the population constraints a little lower, but otherwise, it would be possible. Or would have been possible if we had not already growth to 8 billion.
Conclusion: Hypothetical for between 1.5 and 2 billion population.
All living like the wealthy 1% reality check.
The Earth could sustainably support 3x the number of people living like the wealthiest 1% if they were the only people on the planet.
The key problem is that while the wealthiest 1% are responsible for that huge share of world environmental footprint, they are dependent on populations of billions for the creation of their wealth. Take a wealthy entertainer, sports star or billionaires like Elon Musk, or Jeff Bezos and their wealth would be halved if the population was halved. The wealth of the wealthiest 1% depends on people who crate that wealth, and build and provided the assets and services they use that wealth to enjoy.
But need dependence on the masses always be the case? AI provides the potential for all the world’s housing, cars, computers and other goods to be constructed without human labour and all the world’s food to farmed without human labour. AI means all the wealth enjoyed by the wealthiest 1% could one day be provided without the need for a supporting population. This would completely rewrite the rules on how the wealth is established as it could no longer result from “the masses”, but in a world of artificial intelligence and robots, a super wealthy existence for perhaps 240 million individuals could be sustainable. As more and more power rests in the hands of the extremely wealthy in the “Bangaldesh” scenario playing out in many countries right now, the risk of this dystopia increases.
If we are worried about AI making humans obsolete, perhaps we should be more worried about a super wealthy upper class using AI to make the rest of humanity obsolete.
Conclusion: Hypothetical unless AI is used for a takeover for less than 0.5 billion population.
Overview: Maximising overall happiness and/or economic output vs the individual experience.
Strangely, the position modern society typically applies to chickens in an egg farm is often not applied to population goals for humans. The organic egg farm would fail tests many see as critical for optimum human population, where:
- An increase total economic output is seen as sufficient justification for population increase.
- Low living standards can be seen as acceptable if that allows for a population increase.
In some ways, with that same attitude the near elimination of childhood mortality could be seen as mistake, since the children who previously died at a young age at least were able to live a short time. Similarly, following the logic to its conclusion, would be to recommend ending the lives of the elderly or and those who become disabled, in order that the resources these people would use can instead be utilised to provide for a greater population.
There is an argument that twice the people living with half the happiness is a greater amount of total happiness, yet we do not accept that for the chickens, or to excuse animals born only to be used in laboratory experiments who would suffer in those experiments.
I did have a dilemma deciding between allowing more people to live and allowing those who live to have a better life, which for me is resolved by focusing on the goal of extending the total number of people who can ever live by focusing on the solutions to extending the time and locations for people to be able to live beyond the constraints of one finite planet.
Individual vs total happiness: Millian vs The Benthamite criterion.
Probably the most diffused approaches (at least in macroeconomic theory) are average and total (or classical)Reassessing Edgeworth’s Conjecture when Population Dynamics is Stochastic: Simone Marsiglio
utilitarianism, respectively based on the so-called Millian and Benthamite criterion. The former says that
social welfare coincides with per-capita utility while the latter that social welfare is the sum of individual
utility across the population (per-capita utility multiplied by the population size, if agents are homogeneous).
Focusing on growth for the total economy.
Two possible population outcomes from following the “whatever is best for the economy” have already been explored in “Bangladesh” and “Wealthy 1%” above. While both have dystopian downsides for most people, they could be the future.
… more to be added.
- Optimum Population: An Introduction, Klaus F. Zimmermann
- Economic discussion: The Optimum Theory of Population
- Encyplopedia.com: OPTIMUM POPULATION
- to be added
- 2023 July 23 : Added ecological footprint and sustainability data.
- 2023 April 10 th: first published, but with much still to be added.