The UN population report: misunderstood and misused

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[The follow-up to this essay is here.]

In 2004 the United Nations issued a report titled World Population to 2300. (Large pdf) In it, the demographers who authored the report offer “projections” concerning world population growth through this century and all the way to 2300. The following graph, based on the UN’s, shows the three scenarios or projections for which the report is best known. As you can see, their medium scenario, the one on which most people focus, shows what might appear to be a near peaking of population growth around 2050:

Graph of UN data

I had occasion last year to sit in on a college class in which the students were discussing the issue of world population growth. One student asked the question, “Why should we worry about population growth when the UN says world population will stabilize around 2050?” That’s an important question, and one the student is not alone in having asked. The UN report is cited from time to time by mainstream economists and others who dismiss concern over population growth. (Sometimes those on the far right voice instead a kind of corporate concern about the slowing of population growth in developed countries. That is a topic for a future post.)

Do they have a point? Should we take comfort in UN report? Should we see it as reason to dismiss, at least to some extent, population growth as a serious concern? I will try here to show why that would be a mistake. To understand why, we have to look closely at the report to understand what it really says and to recognize its limitations.

The report is a large document, attached to which are 12 supplementary essays by an array of authors. I won’t attempt a thorough critique of it here. To do it any justice at all, in fact, would take a long essay, much longer than the already-too-long-for-the-blogosphere essay you’re reading now. (I promise shorter posts to come!) Instead, I’ll address certain aspects of the report in this and one or two subsequent posts (not necessarily appearing consecutively), all aimed at answering the question, “Should the UN report’s projections be of any comfort to those concerned about population growth?”

First, I should note, for the sake of accuracy, that the medium scenario does not, in fact, have world population peaking in 2050. It has it continuing to grow until a peak of 9.22 billion in 2075. That people frequently refer to a peak in 2050 is, I think, a result of the graph above ending at 2050, as well as a fair bit of talk in the report about projections to 2050.

What are those “projections,” really?

To begin forming an answer we must examine the nature of those projections. We need to consider carefully what the authors say about this issue. Let’s look at a few points made in the report’s introduction. There, the authors first say:

This report presents projections of world population, and even of the populations of individual countries, over the next 300 years. Given the inherent impossibility of such an exercise, these projections have a special character. They are not forecasts. They do not say that population is expected to reach the projected levels. Rather, they are extrapolations of current trends. They give what paths population would follow if, and only if, historical trends and trends previously forecast up to 2050 continue. Of course one cannot expect these trends to continue as is… (emphasis added, p. 3)

They are telling us, then, that their “projections” are not the predictions most assume them to be. They explain in several places that they are merely plausible scenarios, given certain fixed assumptions derived from observations of recent history, assumptions the authors make clear will almost certainly not match reality. The medium scenario is not a “best guess.” It is simply one scenario, albeit perhaps more plausible than the high or low scenario.

To emphasize their point, they mention that “constructing long-range projections such as these is a little like predicting the outcome of a basketball game after the first five minutes. No one can do that reliably.” (p. 3)

They add:

[That the report looks at long term implications of short term trends] should not be taken to imply that these trends are actually expected to continue. To some extent, the reverse is true. The projected long-range path for population is reported partly to facilitate thinking about how to prepare for it, but also to encourage action to modify this path, to make it more favourable… (p. 3)

If one were to attempt to use the projections as predictions, one would run into problems as “Projected figures for the near term (say up to around 2010) benefit from the accuracy of base data and are unlikely to be off by much. Projected figures for 2050, in contrast, are much less certain.” (emphasis added, p. 4) (Note that such a statement momentarily strays from the recognition that these projections are not intended as predictions. My guess it that even for some associated with the report, maintaining that clarity of purpose was not always easy.)

The unknowable

Divining the unknowable

The supplementary essays shed further light on the nature and limits of the document. We can glean a good deal even from the title of Michael S. Teitelbaum’s, “Projecting the Unknowable: A Professional Effort Sure to be Misinterpreted.” Continuing on to the content we find first the caution that “the core goals of the effort might be described as located somewhere on a continuum between the Implausible and the Impossible. The truth is that none of us has the ability to see very far into the future…” (p. 165) And again, “[The projections] can be understood only as hypothetical scenarios, and not as forecasts.” (p. 166)

To underline his point, Teitelbaum adds:

“The truth is that much about the future of demographic trends a century (or three centuries) from now is unknowable, and quite literally so. None of us has any way of detecting whether fertility rates over the coming century will be lower or higher than at present, nor whether erratic/unstable or fluctuate in some stable and predictable way.” (p. 166)

Teitelbaum offers an illuminating analogy: “Consider what range of ‘plausible’ 300-year demographic projections a sophisticated statistician in 1700 might have developed for the year 2000.” (p. 167) Nor, he adds, could a demographer in 1900 have made a 100 year projection with much greater confidence. Similarly, focusing only on the UN’s projections through 2075 — the year in which world population is projected to peak — we might consider the ability of a demographer in 1933 trying to project demographic trends through 2004. As Teitelbaum suggests, the United States baby boom, alone, would have been completely unforeseeable.

Reminding us of what the projections are, Teitelbaum argues:

[They] can be understood only as hypothetical scenarios, and not as forecasts. The word scenario (from the Latin scaenarium, a place for erecting stages) is defined as “a sequence of events especially when imagined; especially: an account or synopsis of a possible course of action or events” In contrast, “forecast” has a far stronger assurance of plausibility, of predicting future events on the basis of credible information… (p. 166)

Writing before the report was published, Teitelbaum even recommended that its language be carefully calculated to avoid the impression that the projections were forecasts or predictions: “Avoid use of the indicative future tense, such as ‘will be’ or ‘will increase to.’ Also, “Avoid use of the verb ‘to project,’ as in ‘We project that…’ This formulation often is misunderstood by non-technical readers to mean the same as ‘We predict that…'” (p. 167)

Reading through the report reveals that Teitelbaum’s recommendations were essentially ignored, contributing heavily, no doubt, to the frequent misuse of the report’s data.

Irresistible misinterpretation

Irresistible

We are cautioned still further in the essay, “Foretelling the Future,” by John R. Wilmoth:

Even with proper warnings, I think that both projections and forecasts are often interpreted as predictions of the future in the mind of the average listener. Furthermore, most people are unlikely to notice anything more than the “medium variant,” which they see as a professional’s “best guess” concerning future demographic trends. Although some may take note of the uncertainty implied by presenting multiple variants, I believe from experience that even the most sophisticated consumers of such information do not see demographic projections and forecasts as mere illustrations of possible future paths for the world’s population – in other words, at best they view them as predictions with a degree of uncertainty. Perhaps this issue could have been addressed most effectively by choosing a different title for the report and then stating clearly the motivation behind this unusual exercise… (pp. 174-175)

Small differences lead to big differences

Part of the difficulty of predicting future population size, and adding to why the authors did not attempt such prediction, is described in the essay by Tim Dyson: “Small but sustained deviations in total fertility result in big differences in eventual population size – e.g. in the low scenario, in which total fertility is essentially 0.25 of a birth lower than in the medium scenario, the world’s population in 2300 is only 2.3 billion (compared to 9.0 billion)” Demographers have enough uncertainty to deal with in trying only to anticipate widely divergent fertility rates. To attempt to differentiate between possibilities varying by small fractions of a percent would be folly. Yet, as Dyson suggests, those small, unpredictable differences add up in time to huge differences in population numbers.

Then what’s the point of the thing?

What then is the use of the UN report? Simply, it allows us to consider current data, to compare how plausible futures would vary as a function of different assumptions. It enables us to consider “what if” scenarios, to ask, “What if recent trends were to continue? Would they necessitate action on our part? Do they suggest we would be headed for problems? Do they point to anything alarming enough that we might consider taking certain actions now?”

There are far too many social and otherwise complex elements at work in population growth to allow for any sort of reliable predictions at this stage in the demographer’s craft. Joel Cohen, mathematician and author of the book, How Many People Can The Earth Support? sums it up: “demographers are better at forecasting the demographic consequences of choices people might make about fertility and mortality and migration than at predicting what those choices will be.”

Just from this examination of the nature of the UN report’s projections, then, we can see that it would be a mistake to say, “The UN says world population is going to peak around 2075,” much less to add that “Therefore, there’s nothing to worry about.” Simply put, the UN says neither.

There are other reasons why such statements are mistaken. We’ll look at those in the near future.

[The follow-up to this essay is here.]
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22 responses to “The UN population report: misunderstood and misused

  1. great article.
    i come from a country which is expected to contain the world’s largest population a few years from now, and i have had very similar discussions with my friends, on whats the point of discussing about population.
    the second thing is that it is the in-thing in India to discuss about the demographic dividend our country will receive thanx to our young population, which according to me is more bullshit than true.
    one more thing. we are here talking about the stabilization of world population, not about stabilisation of population in individual countries. surely, population remains a big concern, because of that reason also.

  2. “much longer than the already-too-long-for-the-blogosphere essay you’re reading now. (I promise shorter posts to come!)”

    Hi John, agree with the above ;), but it was informative and I learned from it.

    Perhaps you should consider summarizing these longer blogposts into something more quickly absorbed by the newer generations of shorter attention spans.

    But very nice!!

    I was thinking of asking you/anyone to comment on a newspaper column (same author as that one I emailed you recently.), but they seem so mindless compared to what you have here.

    Ross

  3. unnati,

    Interesting perspective. I am from Canada which has a very small population compared to land mass.
    So it’s hard for someone like me to personally feel the situation.

    Ross

  4. unnati,

    Thanks for your thoughts. (I just got back online after some sort of day long outage at my ISP.)

    You said,

    “we are here talking about the stabilization of world population, not about stabilisation of population in individual countries. surely, population remains a big concern, because of that reason also.”

    That’s a *very* good point, I think. I see some economics writers (usually those of a fairly “right wing” slant from places like the American Enterprise Institute) complaining about the “problem” of population loss in European countries, Japan, etc. Others try to dismiss population growth as a problem on the basis that some countries currently have fertility rates near the replacement level. But, as you point out, we’re not talking about “some countries” here; we’re talking about *world* population growth. And if certain pieces of land have more slowly growing populations, that’s not a lot of comfort for the world as a whole, which is still seeing its population growing at a fast clip.

    signature103, who just posted a comment on another article here, has a nice post about this very topic on his blog. It concerns attitudes about the sub-replacement fertility rates in Japan.

    I was just exploring your blog, and look forward to reading more!

  5. Ross,

    Yeah, I like your suggestion to add a brief summary to the longer posts. But my wife said, “Well, you have a more sophisticated readership than the average blog. They won’t mind the longer posts so much.” 🙂

    I’d like to see the article you mention. If you can email it to me, I’ll gladly read it. I’m wondering if it’s one of the articles you see these days about the threat of population *loss*. These strike me as so absurd at a time when world population is still rising quickly. That, plus a reduction over time of world population, and even in the populations of many or most countries should be a beneficial thing, though some adjustments would be necessary. Present population levels have already done a lot of damage, and the alternative of endless growth is just ridiculous. Much better to learn how to adjust to shrinking populations than to try to cope with further growth.

  6. You might be interested in a couple of related posts I did at http://facilitatedsystems.com/weblog/2007/01/inaction-in-face-of-uncertainty.html and http://facilitatedsystems.com/weblog/2005/03/not-good-news-what-do-we-do-about-it.html

    The latter points to a PNAS article that helps address the issue of why it matters. If those authors are correct, we’re already above the carrying capacity of the earth. The former points to two arguments in favor of doing something sooner rather than later when the potential consequences of doing nothing are great.

  7. Thanks Bill. Some excellent links there. Lines like, “The report says humans have changed ecosystems more rapidly in the past 50 years than any other period,” have become all too common.

    Interesting to see that the PNAS article is featurs Wackernagel’s work. I know he created the “ecological footprint” model which has been very well received. It was used by the authors of Limits to Growth: The 30-Year Update as well.

  8. Yeah Bill, I think the Limits to Growth work is some of the best out there. In fact, I just recently posted something to that effect at another blog. 🙂

    BTW, your comments are, for some reason, getting snagged by the spam filter. I have no idea why. And it may clear up as I keep marking them “not spam.” But just know there could be some delays for a while between your commenting and it showing up on the site. (as I just send it through as soon as I see it)

  9. John, thanks for the heads up. I don’t think I’m doing anything that would attract the attention of a spam filter, but who knows.

    Given the title of your blog, I thought you might be interested in a few postings I made last year on growth. Perhaps the easiest way to find the more popular ones is to look at items 2 and 6 of my “Top postings of 2006” (I already mentioned item 3). A blog search will turn up a few more.

    I suspect we largely agree, but we may have areas where differences could stimulate good thinking and dialog. Thoughts?

  10. Thanks Bill. I don’t see much I disagree with there. Interesting to see these ideas concerning growth applied to businesses. Most of my attention regarding economic growth, of late, has been on the big picture — more or less the level of policy at the state or national (or international) level. But I certainly agree with your suggestion that an organization shouldn’t become fixed on growth as a goal in itself. The whole growth imperative is so pervasive that few stop to question its logic. They’re too busy chasing growth! I’ll need to read further on your blog, for sure.

    It’s not unlike cities and towns which look to growth as some sort of key to prosperity — an unsustainable strategy, to say the least. (One of your posts, btw, linked to my old blog which focused on urban growth. 🙂

  11. John, I wonder if one of the problems is fear and uncertainty: how can one create a viable economy that’s not based on incessant growth? I suspect we don’t know the answer and may fear taking the time to think it through, thus taking time away from keeping the growth going.

  12. I think that’s about it, Bill. It seems to me there needs to be some sort of large scale project aimed at answering that very question. Bring in the steady staters and eco-economists and, okay, even some enviro-economists and anyone else who offers a potential alternative. See what they come up with. Well, there could be other ways of going about it, but we need something.

    Of course the first step, really, is getting enough people to question the need and benefits and logic of perpetual growth. There are over 600,000 blogs on wordpress.com. Maybe I’ll go on their support forums and suggest that 1/6 of them become “anti-growth” blogs. 😉 I think then we’d see lots and lots of action on this. :-/

  13. Ross wrote:

    “Interesting perspective. I am from Canada which has a very small population compared to land mass.
    So it’s hard for someone like me to personally feel the situation.”

    – —

    This is an interesting point of view. And quite understandable, too. This perspective is the one that is making it hard for people to connect with the problem of overpopulation, ’cause what does it mean to “feel the situation”?

    On a local level, overpopulation is a problem that is rarely felt. I mean: there’s hardly any such thing as a discussion about local over-population, even in cities like London and New York! Even though very congested cities often (and due to overpopulation) have very low air and tap water quality, these issues are not seen as “problems” but “challenges”.

    IN parts of West- And Central-Africa, erosion of the land has become a problem that is seen as closely connected with over-population. But even there, it is seen as more of a challenge than a problem. – Along with local environmental problems such as deforestation, desertification, dwindling water resources, growing urban slum areas, open sewers, etc. – All these are seen as challenges, and not as problems.

    It is very important for people to understand that the REAL PROBLEM with the population explosion is … (almost) all in the air …

    We live today on a positively fossil-fuelled planet which is about to become over-industrialized and therefore also over-polluted by a human species which is expanding in numbers at a somewhat parasitic rate (if you know what I mean by that?) … :/

    The population explosion, as coupled up with fossil-fuelled industrialization, enhanced greenhose effect and global warming, gives spark to extreme weather patterns (short term) and climate change (long term).

    Scary, huh?!

  14. Magne,

    You make some very, very good points there. I just wanted to add that in addition to climate change issues related to the burning of fossil fuels, population growth is closely tied to a number of other environmental problems. (I guess, really, it’s tied to most of them to one degree or another.) Many experts, such as the authors of Limits to Growth: The 30-Year Update, believe we will have growing difficulty producing enough food as the population grows to 7 billion and beyond, and there are clear issues concerning overfishing, deforestation and other problems.

    But I agree that climate change may prove to be the most pervasive problem as it’s global in its reach and is going to affect people just about everywhere. Also, it’s tied to a lot of other problems such as the loss of coral reefs. (a very serious problem right now)

    Thanks for you input! Gotta go, but I’ll try to reply to your other recent comments a little later.

  15. Magne Karlsen

    I once read that the farmers of this world are currently producing enough food to feeding about 12 billion people. Yet people are still starving, because lots of this food is used for feeding animals while another lot of it is simply thrown away.

    Some deforestation takes place because growing populations need to clear new land for farming and housing, but the most important (and most destructive) forms of deforestation come as a result of these good old nasty themes: economic interest, stupidity, and greed. – The same can be said about overfishing.

    Deforestation and overfishing is big business. The companies involved are looking to secure short term profits, >> and that: as fast as they possibly can. The workers are in on it, because they, too, are looking to make as much money as possible at the fastest possible rate.

    It’s been mentioned before, and I’m telling you again: this civilization is completely crazy. The current dollar frenzy is absolutely insane.

    Just consider the shark fin industry! Here they are: fishermen all over the tropics, killing sharks and merely cutting off the fins, only to throw the fish into the ocean again, to drown and die.

    Why?

    – — – —

    Anyway.

    When it comes to the Malthusian argument, I don’t believe it can survive a reality check. As we become more people, more food seems to be produced.

    I believe the problem of a basic lack of food may only come as a result of serious climate change, resulting in longer and more frequent periods of draught (or floods) in the important farming regions of this world. – Unfortunately, as seen over the last few years, the development seems to go in this direction.

  16. Magne,

    I only have time for this comment right now, but I’ll try to get to the others tomorrow.

    I do certainly agree about the dollar frenzy. But I also think the Malthusian argument concerning food is more robust than it may seem. 🙂 I’d have to go back to review the details, but the basic kind of data I was referring to in Limits to Growth: The 30-Year Update were indications, for example, that while total world grain production has continued to rise (though it’s hard to tell if it’s leveling out now), per person production peaked in the mid 1980s and has declined slightly since. Yes, for now there is still enough food production to feed everyone adequately in theory (though I wonder if the 12 billion figure was talking about a very meager, subsistence level diet), but as you point out, a lot of factors intervene to prevent it. Then, considering that trend and adding in continuing population growth at the same time as possible per-hectare yield plateaus in some grains, water issues, soil erosion, and projections of the amount of land needed to feed the increasing population, and it appears we could reach or surpass even the number we can feed “in theory.”

    And then there’s the climate change contribution you mention. (separate from the Malthusian angle) It doesn’t look good.

    On deforestation I don’t think we disagree too much. I’d just emphasize the role of population a bit more as mentioned here. Okay, more later. 🙂

  17. Magne Karlsen

    John,

    I don’t think we disagree too much at any note. 🙂

    I read your stuff, and my knowledge expands. If some of my remarks can help you expand your knowledge, I guess that’s what I’d call a win-win situation for both of us. You see: there’s such a grand number of key factors; it is obvious that it must be difficult for any one person to keeping track of them all.

    Thanks.

  18. Magne,

    You’re definitely helping me expand my knowledge! 🙂 Your comments have lead me to think and research, and remind me how complex a lot of this is. As you say, there are so many factors it’s hard to keep track of them and all their interrelationships. (”Wait a minute, is this problem caused by population or economic growth, or consumption, or what combination…?”) With regard to population, I’ve been trying to collect some sources concerning the various population-environment linkages. One handy place for a quick overview is here:

    http://www.ucsusa.org/ssi/biodiversity/population-and-environment-linkages.html

    I’ll be pulling more together on the “All Links” page I’m working on. And I welcome any links you have or that you come across.

  19. Magne Karlsen

    http://media.wiley.com/product_data/excerpt/75/04717474/0471747475.pdf

    http://www.blueprinttoabillion.com/BPTAB_FrontMatter.pdf

    PDF files: “The Blueprint Thesis: a different approach to growth” – a thesis (by David G. Thomson) exploring the essentials involved in achieving the goal of “exponential revenue growth”.

  20. Magne,

    Thanks for those. “Exponential revenue growth”… hmmm. Definitely some insights into the growth imperative there, I suspect.

    I don’t know, I always kind of felt I’d be content after that first hundred million. But no, maybe a billion is *essential* to my happiness. 😉

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