World population grew by almost 300% during the twentieth century; over the same time period, world per capita incomes grew by about 400%. This association of sizable increases in world population with large increases in per capita incomes should continue to the end of this century.
Forecasts of the world’s population only a few years in the future are generally quite accurate because the number of births and deaths during the next few years are largely determined by the existing distribution of the number of people at different ages. At the same time, forecasts of the population 50 or more years into the future are notoriously inaccurate because of difficulties in predicting changes over a long time period in birth rates, and to a much lesser extent, also in death rates.
In particular, one cannot take seriously the UN’s median forecast of 10 billion persons by the end of the century. For this forecast assumes that birth rates in high fertility countries will not decline during the next half-century. Since it is highly likely that these countries will raise significantly their per capita incomes and education of their women, their fertility rates will fall, probably drastically. If so, world population in 2100 would be well below 10 billion people.
However, for the sake of this discussion, I assume that the UN forecast is approximately correct, so that about 10 billion people will inhabit the earth by the end of this century. Posner mentions various likely benefits of a much larger population, such as greater demand for and supply of innovations in the medical and other sectors, and greater world specialization by skill.
Few countries have experienced sustained declines in their populations since the beginning of the 19th century. 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. If I am correct, countries such as Russia, Japan, and Germany, with fertility rates that are far below replacement levels are likely to face an unattractive economic future unless either they take in enough immigrants to make up for their low fertility levels, or they have large increases in fertility rates.
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. This could produce a water shortage unless countries began to price more efficiently the water used in agriculture and industry, by far the largest water users. With sensible prices, the available water should be sufficient to satisfy all essential water needs of a much larger world population.
An increase from 7 to 10 billion people on the planet will significantly raise population density in many parts of the world, and thereby increase the potential for severe outbreaks of communicable diseases. However, cities like Hong Kong show that it is possible even with current knowledge to control the spread of disease in densely populated communities. As knowledge of how to track and combat diseases greatly improves over time, the medical challenges created by densely populated areas should be reduced even further.
A larger population combined with growing per capita incomes would increase global warming and worldwide pollution. Although the severity of the global warming problem by the end of this century is not fully established by climate science, the 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 (see the analysis in Becker, Murphy, and Topel, “On the Economics of Climate Policy”, The B.E. Journal of Economic Analysis and Policy, Volume 10, number 2). 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.
Good luck with all of that, Professor.
Posted by: Jim | 05/08/2011 at 03:49 PM
Were you aware that the world has consumed more grain than it's produced 11 out of the last 13 years?
Posted by: Root Hoi | 05/08/2011 at 10:15 PM
Intensive agriculture poses significant environmental costs, that above some threshold pose significant long-term costs. For example, a great deal of the agricultural land of California's central valley are experiencing rising salt contents, which make the land far less productive. Similarly, intensive pig and chicken farming waste can have a negative impact on our fisheries. Agricultural production is not geared to highest production per acre/hectare, but to the lowest cost/unit product per acre. This fact can be readily attested to by a visual comparison of an well-tended garden and a typical crop field laid out in neatly spaced rows.
Posted by: Uiop | 05/08/2011 at 11:51 PM
em...., very insteresting article. thanks for you hard work.
Posted by: denis | 05/09/2011 at 02:06 AM
It's likely to require substantial C H A N G E if it works at all.
Here's a bit on the non-health of our Ogallala Acquifer:
http://webcache.googleusercontent.com/search?q=cache:coWJnnxGhn8J:en.wikipedia.org/wiki/Ogallala_Aquifer+ogallala+aquifer+depletion+rate&cd=1&hl=en&ct=clnk&gl=us&source=www.google.com
...... and with systems highly stressed the breakdowns are likely to be spotty and perhaps sudden.
In a QA session after a panel exploring the myriad nuances of the Pakistan, Afghanistan, bin Laden affair, one questioner said I've three, one word questions not covered: Food. Water. and Opium.
Aaah, yes! If a democratic or other system does not provide even the basics as it strives to build a wealthier capitalist or mixed economy, there's not likely to be a peace in which to build it.
Posted by: Jack | 05/09/2011 at 07:14 PM
Uiop...... and we do have the potential to switch from growing, costly to maintain and useless, turf to truck gardens! Where's qwerty?
Posted by: Jack | 05/09/2011 at 07:18 PM
qwerty is in my left hand, Jack. But I'm not sure I understand your comment. Local farming works well enough, but international distribution of some crop foods is necessary to counteract local shortages, especially grain crops. Certain modes of farming are labor intensive. We don't have peasants any more for a reason.
Posted by: Uiop | 05/09/2011 at 10:01 PM
Uiop -- Clarification: I was commenting on the immense wasted potential of suburban lawns -- a COSTLY crop that is over-fertilized, screws up the streams, and is hauled off to a land-fill at yet more cost.
I was reflecting on nations like Korea where a sidewalk sized patch of land outside a factory fence will be planted in green onions or some such. During WWII we had Victory gardens when every little bit helped.
But yes...... even home grown carrots, though tasty, are typically not competitive with "storebought".
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Posted by: Okucia meblowe | 05/13/2011 at 05:45 AM
Ample resources for ten billion people by year 2100? We're beginning to see and have problems supplying clean water for the current seven billion that now inhabit the planet. In some circles, there is talk of beginning to pump down the Great Lakes in the U.S. and I won't even mention the draw down of the Aral Sea, or that lake in California that has become nothing less than a salt pan. As for the World's Aquifiers, the well strings are now having to be pulled and the wells drilled deeper and deeper every year.
One solution, "Ocean based Desalination Plants". But then, due to tax cuts and the like, we can't even afford to maintain and upgrade the infrastructure we already have. Let alone spend hundreds of billions needed to establish a new infrastructure to supply clean water. One of the basic essentials of life on the Planet...
Posted by: NEH | 05/15/2011 at 09:29 AM
we can't even afford to maintain and upgrade the infrastructure we already have. Let alone spend hundreds of billions needed to establish a new infrastructure to supply clean water. One of the basic essentials of life on the Planet...
Posted by: christian louboutin | 05/15/2011 at 09:52 PM
Have you given any thought to the problems raised by Lester Brown in his well researched books and this month's article in "Foreign Affairs" about how virtually all arable land is now being utilized to its' full capacity based upon the availability of water. Also, he points out that both the Colorado and Nile rivers are now being fully utilized by their adjoining states or countries and most years their waters have not reached the oceans. I would like to hear your response to the notion that water and food set the limits on population growth.
Posted by: Ken Leonard | 05/19/2011 at 05:11 PM
Forecasts of the world’s population only a few years in the future are generally quite accurate because the number of births and deaths during the next few years are largely determined by the existing distribution of the number of people at different ages. At the same time, forecasts of the population 50 or more years into the future are notoriously inaccurate because of difficulties in predicting changes over a long time period in birth rates, and to a much lesser extent
Posted by: Rosetta Stone | 05/21/2011 at 02:39 AM
Forecasts of the world’s population only a few years in the future are generally quite accurate because the number of births and deaths during the next few years are largely determined by the existing distribution of the number of people at different ages.
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Posted by: Red Bottom Shoes | 05/25/2011 at 10:58 PM
This guy is not an earth or environmental scientist. Why does he think he knows a darn thing about this topic? I think he should ask someone who is actually an expert on matters of the effect of pop. growth on the environment. That person would say, less population is better for the world, all else equal.
Listen to an expert, not to a law professor.
Posted by: T-Dog | 05/26/2011 at 04:46 PM
Also, he points out that both the Colorado and Nile rivers are now being fully utilized by their adjoining states or countries and most years their waters have not reached the oceans. I would like to hear your response to the notion that water and food set the limits on population growth.
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