Bryan Caplan  

Posner and Becker on 10 Billion People

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Posner's a nervous optimist:

But suppose world population will reach 10.1 billion by the end of this century. Would that be a good or a bad thing? Arguably a good thing, on several grounds. One is that it would enable greater specialization, which reduces costs. Second is that it would increase the returns to innovation by increasing the size of markets, though an offset is that innovation can produce immensely destructive as well as constructive technology. Third, the more people there will be, the more high-IQ people there will be, and hence the faster the growth of knowledge will be; though a possible offset is that the more evil geniuses and other monsters there also will be; persons of great potential for evil, such as Hitler, Stalin, and Mao, presumably are rare...*

The downside of population growth is the pressure it places on the environment and natural resources, especially the former, since the price system provides efficient rationing of resource use... Continued population growth could combine with an acceleration of global warming to precipitate a global catastrophe (perhaps a catastrophic water shortage) within the next few decades, but 89 years from now the march of technology may enable such problems to be solved. Think of the technological advances of the last 89 years (that is, since 1922), and imagine a comparable rate of technological advance applied to the current level of technology, which is so much higher than that of 1922. 

But the beneficent effects of population growth, like the estimates of that growth, are highly uncertain. The risk averse among us might prefer a lower rate of population growth in order to reduce the downside risks of that growth, even though the upside potential would be reduced as well.

Becker's a calm optimist:
The substantial world growth in per capita incomes during the past 150 years has been associated with growing world populations. I believe that declining populations are bad for long run economic welfare...

Given the sharp rise in food prices during this first decade of the 21st century, it would appear difficult to feed adequately a much larger and richer world population. Yet, unlike say the production of copper, no natural limits sharply curtail the amounts of food that can be produced. Food output will expand with a growth in the amount of land devoted to food production-currently agriculture takes a small fraction of the world's arable land. Also, the world can invest much more in fertilizers and in improving food technology, so that greater output can be squeezed out of each acre used to grow corn, wheat, soy, dairy, meats, and other foods.

Greater demand for water due to larger populations and greater wealth would make clean water scarcer... [But] With sensible prices, the available water should be sufficient to satisfy all essential water needs of a much larger world population.

[...]

A larger population combined with growing per capita incomes would increase global warming and worldwide pollution... [T]he world should be prepared to meet various worst-case climate scenarios. This would require the development of mitigation techniques that can be rather quickly ramped up in case global warming turns out to be a severe problem... Such technologies are certainly achievable by the end of the century with substantial private and public investments in developing new methods to capture and store various harmful gases emitted by fossil fuels.

If world population grew to 10 billion by the end of the century-an unlikely outcome- that would present considerable challenges. However, greater population would add real benefits as well, and I am inclined toward the view that the benefits will exceed the harm.

Both more reasonable by far than Bad Religion's "10 in 2010," but the song's too singable to hate.

* I make the same point at greater length here.



COMMENTS (20 to date)
Bo writes:

Nice Bad Religion reference! I always wondered if they'd change that song at concerts since they missed the mark so badly.

Lord writes:

How about a realist. If what has to happen doesn't, famine, disease, pestilence, and war will solve our problems.

Julien Couvreur writes:

One thing that bothers me with this whole debate is the un-spoken question. What is the optimal human population?

Isn't that question similar to asking what is the optimal production of shoes, which we know it cannot be centrally answered?

Both sides bring up valid arguments (such as: more people bring more invention, but more people also consume more resources). But that does not mean that more is always better, or less is always better. Such analysis cannot provide the optimal number of shoes and neither can it provide the optimal human population.

Maybe we're asking the wrong question, or at least an invalid one. Optimal for what?

George writes:

Water resources are controlled (in the main) by government agencies, or local government-granted monopolies. I am certain that competitive privatization of the supply and distribution of water should, in the long run, alleviate water shortages. People who are used to mis-priced water may not like the near and mid-term water prices, but perennial battles over access to water in many regions of the country and around the world will disapear.

quadrupole writes:

I am stunned that someone can worry about a shortage of water on a planet with 75% of it's surface covered in the stuff.

The real concern is energy. Given enough energy the water can be purified to be potable.

Evan writes:
One thing that bothers me with this whole debate is the un-spoken question. What is the optimal human population?....Maybe we're asking the wrong question, or at least an invalid one. Optimal for what?
This isn't really an answerable question because the humans are valuable for their own sake. Optimal production generally refers to how much stuff you need to make to serve a human's value.

You could set up a number of goals and try to determine what the optimal number of humans needed to accomplish that goal is, but people's goals vary. Preserving the environment, probably a lot less people. For space colonization we'd need trillions.

Lint writes:

I know it's already been said, but kudos for the Bad Religion reference.

Steve Sailer writes:

"Third, the more people there will be, the more high-IQ people there will be ..."

Not necessarily.

Andy writes:

From data I've seen we could feed 10 billion people without expanding the amount of land used for agriculture simply by adopting more efficient techniques more broadly. This doesn't even include the extremely likely advances in technology that will improve efficiency even further by the time we reach that population.

ERIC writes:

I agree - love the Bad Religion reference!!!

Thomas DeMeo writes:

The big looming challenge will be about substantial improvements in extending life, and how we deal with it.

MTP writes:

I don't know that I agree with Posner's relatively dismissive assertion that no natural limits sharply curtail the amount of food that can be produced. We may not be near such limits, but arable land is finite and the supply of phosphorous for fertilizers is also finite. As the emerging market middle class consumer develops and expands, their diet will consist of relatively more protein, and these animals will at least partially have to be fed with vast amounts of wheat or other proteins thereby creating potentially significant demands on arable land.

Land grabs, diminishing returns to improvements in genetically modifying crops, diminishing nutritional quality of fish and meats due to excessive 'farming', pollution, or unintended consequences of other policies, and other trends probably put me in the nervous camp. Probably also a bit Malthusian as I do think an unsustainable population would adjust downward, but perhaps the price of maintaining what has in recent history been a Western diet (more protein, costly to produce and consume) made affordable by what Jeremy Grantham calls the 'hydrocarbon revolution' will rise enough to offset the secular surge in demand ahead.

Nick Bradley writes:

Water will not be an issue for two reasons:
1. desalinisation is getting cheaper, and
2. we're getting richer

- At 3% real per capita global GDP growth, the world will be 3x richer in 2050 and 14x richer in 2100. If global growth stays at 3% through 2050 then tapers off to 2% for the following 50 years, you're still looking at 8x - 9x growth.

- A proposed desalinization plant in San Diego will sell desalinated water to consumers at $950 an acre-foot (the Israelis can supposedly produce desalinated water at $600/A-F). The San Diego water district pays $700 right now.

Nick Bradley writes:

Water will not be an issue for two reasons:
1. desalinisation is getting cheaper, and
2. we're getting richer

- At 3% real per capita global GDP growth, the world will be 3x richer in 2050 and 14x richer in 2100. If global growth stays at 3% through 2050 then tapers off to 2% for the following 50 years, you're still looking at 8x - 9x growth.

- A proposed desalinization plant in San Diego will sell desalinated water to consumers at $950 an acre-foot (the Israelis can supposedly produce desalinated water at $600/A-F). The San Diego water district pays $700 right now.

Evan writes:

@Steve Sailer

Not necessarily.

If there are a lot more people the absolute number of high-IQ people is likely to go up, even if people reproduce in such a pattern that the percentage of high-IQ people goes down. This is because if low-IQ people reproduce more they are more likely to have children who "buck the trend," "win the genetic lottery" and have a high IQ. Of course, the majority of their children would have low IQs, but the absolute number of high-IQ people would have gone up.

Creativity and wealth comes from the absolute number of high-IQ people, not the percentage of high IQ people (that's one of the reasons the USA has a higher GDP per capita than Japan), so Posner's reasoning is sound.

Chris T writes:

What is the optimal human population?

The problem with this question as stated is it's utterly meaningless. What is the optimal human population for what? Under what conditions? Over what length of time?

The real concern is energy. Given enough energy the water can be purified to be potable.

Given enough energy virtually anything becomes possible. In fact, technological advance can be defined as nothing but humans gaining access to and making better use of energy.

Nick Bradley writes:

@ Chris T -

"In fact, technological advance can be defined as nothing but humans gaining access to and making better use of energy."

- I half-agree. It is the access to and making better use of energy...but it is also the accumulation and sharing of knowledge.

Chris T writes:

Nick - I was defining technological advance as more the direct expansion of human technical abilities. It, of course, requires advances in knowledge, but the actual application requires manipulating the material world.

Roger Sweeny writes:

Think of the technological advances of the last 89 years (that is, since 1922), and imagine a comparable rate of technological advance applied to the current level of technology, which is so much higher than that of 1922.

Somewhere in my head, Tyler Cowen is asking, "Is that reasonable to imagine?"

Julien Couvreur writes:

Chris T and Evan, I agree this "What is the optimal human population?" is unanswerable or even meaningless.
Yet it is implied by arguments for or against more population.

We can discuss what the effects are and what challenges such or such population number brings about, but it is meaningless to debate this topic as a some kind of trade-off as if there could be a collective decision on the optimal population.

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